ML12157A427

Attachment 39 to GNRO-2012/00039 - Mp&L (Mississippi Power & Light Company). 1981. Mississippi Power & Light Company, Middle South Energy, Inc., Grand Gulf Nuclear Station Units 1 and 2, Final Environmental Report, Docket Nos. 50-416 and 50

ML12157A427
Person / Time
Site:	Grand Gulf
Issue date:	05/23/2012
From:	Entergy Operations
To:	Office of Nuclear Reactor Regulation
References
GNRO-2012/00039
Download: ML12157A427 (101)

Text

Attachment 39 to GNRO-2012/00039 Attachment 39 to GNRO-2012/00039 MP&L (Mississippi Power & Light Company).

1981. Mississippi Power & Light Company, Middle South Energy, Inc., "Grand Gulf Nuclear Station Units 1 and 2, Final Environmental Report, "Docket Nos. 50-416 and 50-417. December 18,1981.

GG ER 2.2 ECOLOGY 2.2.1 Introduction Preconstruction terrestrial and aquatic ecological field measure-ments were taken by a 12-man biological staff stationed on the Grand Gulf Nuclear Station site from June 1972 through August 1973.During this period seasonal measurements were taken of vegetation, mammals, birds, reptiles, amphibians, and insect pest infestations on and near the site and of fishes, benthos, plankton and water quality in the two onsite oxbow lakes and adjacent Mississippi and Big Black Rivers. Since August 1973, a full time biologist respon-sible for the conduct of the Environmental Protection Program Re-specting Construction, including construction monitoring, has been stationed at the site.This section provides a summary of all pertinent terrestrial and aquatic ecological field data and historical information that has been collected since the inception of the preconstruction environ-mental field measurements programs in 1972. More detailed presenta-tions of the preconstruction field data are contained in the Environ-mental Field Measurements Programs:

Interim Report (July 1973), Interim Report 2 (October 1973), Final Report (December 1973) and Supplementary Report (May 1974 ). Detailed descriptions of the field data and laboratory procedures used during the preconstruction studies are presented in the Environmental Report, Construction Permit Stage, Amendment 2, Item 22, March 1973.2.2.2 Terrestrial Ecology 2.2.2.1 Summary The Grand Gulf site has two general edaphic types, loessial bluffs and alluvial river bottomlands, each supporting a different plant community.

These plant communities provide habitats that meet the vital requirements of the varied fauna present on the site. Periodic flooding of the Mississippi River onto the bottomlands results in the deposition of nutrient-rich materials.

As a result of these nutrient additions, the bottomlands are more productive 1 than the loessial bluffs (Refs. 1 and 2). This inundation, however, creates an unstable environment, particularly for the vegetation; the bottomland plant community, consequently, contains fewer species than does the loessial bluff plant community.

Because of the presence of forests and fields in both the loessial bluffs and the river bottomlands, the site contains four principal terrestrial habitats:

loessial bluff deciduous hardwood forest, loessial bluff fields, bottomland deciduous hardwood forest, and bottomland fields.The forest communities are the largest habitat and prior to ini-tiation of construction covered approximately 1785 acres (80 percent)More productive in the sense that a given area of bottomland can support a greater density of animals compared to an equal area of loessial bluff.2.2-1 GG ER of the 2330-acre site (on June 19, 1974, 164 acres of bottomland were donated to the Grand Gulf Military Park). Of this, approximately 775 acres are loessial bluff forest and about 1010 acres are bottom-land forest. Two oxbow lakes, Hamilton and Gin, are present on the site and cover about 110 acres in the bottomlands.

Approximately 150 acres of the bottomland forest is shrub swamp dominated by black willow and swamp privet. This shrub swamp is located around the peri-phery of Hamilton and Gin Lakes but is most extensive at the northern end of Gin Lake. Most of the land west of the lakes is periodically flooded and supports bottomland hardwoods and herbaceous vegetation.

No marsh community 2 , however, is present on the site.Field studies have resulted in the documentation of the occurence on the Grand Gulf site of at least 420 species of woody and her-baceous plants, 140 species of birds, 31 species of mammals, 34 species of reptiles, and 14 species of amphibians.

Construction activities have resulted in the clearing of approxi-mately 465 acres of which about 75 percent (350 acres) was forested (274 acres of bluff forest and 76 acres of bottomland forest).One endangered species, the American alligator (Alligator mississipiensis) is present in the oxbow lakes on the site.2.2.2.2 Vegetation Systematic sampling of the forest overstory was conducted in 0.1-acre plots and the understory vegetation was sampled in mil-acre (0.001-acre) plots. Sample plots were established at 5-chain intervals (330 feet) along parallel transect lines spaced approxi-mately 1000 feet apart. Vegetation sampling locations are shown in Figure 2.2-1.During 1972 and 1973, seasonal sampling and continuous collection indicated that at least 420 species of vascular plants representing 285 genera and 105 families occurred on the Grand Gulf site. Sixty-four species (15 percent of the total) were trees. With the exception of three species, all trees occurring on the site were deciduous.

The species composition of understory vegetation grow-ing on the site varied seasonally with the largest number of plants occurring during the summer.None of the species found growing on the site were listed in the"Report on Endangered and Threatened Plant Species of the United States" that was published by the U.S. Fish and Wildlife Service in the July 1, 1975 Federal Register or on the proposed list of"Endangered and Threatened Plant Species" published in the June 16, 1976 Federal Register.2 The existence of a marsh community is determined by the pre-sence of indicative vegetation such as bulrushes, spike rushes, cattails or reeds.2.2-2 GG ER 2.2.2.2.1 Forest Overstory Two forest types occur on the site: bottomland deciduous hardwood and loessial bluff deciduous hardwood.

The bottomland hardwood forest covered approximately 1010 acres (43 percent of the site)along the east bank of the Mississippi River. The bluff hardwood forest covered approximately 775 acres (33 percent of the site)east of and adjacent to the bottomland forest. A type map showing the preconstruction distribution of the dominant species comprising the forest overstory is presented in Figure 2.2-2.a. Bottomland Forest Twenty-seven tree species were identified in the bottom-land forest. Sampling indicated a density of approximately 146 trees per acre and a total basal area of about 61 square feet per acre. Sugarberry (Celtis laevigata), pecans (Carya spp.), green ash (Fraxinus Pennsylvanica), black willow (Salix nigra), swamp privet (Forestiera acuminata), and box elder (Acer Negundo) were the dominant species. These trees comprised approximately 79 percent of the total basal area and about 84 percent of the total number of trees. Swamp privet was the only dominant tree species that is not commercially valuable (Ref. 3).Four species of trees observed in the bottomlands but not encountered in sampling were catalpa (Catalpa bignonioides), mimosa (Albizzia Julibrissin), sandbar willow (Salix interior), and tupelo gum (Nyssa sylvatica).

The catalpa and mimosa trees were found growing near a house and had probably been planted as ornamentals.

As its name implies, sandbar willow grows on sandbars along river and stream banks; onsite, a few specimens of this species occurred along the banks of the Missis-sippi River. Only a single specimen of tupelo gum, a species commonly occurring in the Mississippi River bottomlands, was observed on the site. This species is intolerant of shade and cannot compete with other bottom-land trees. It typically occurs on very wet sites where most other species cannot survive.b. Bluff Forest Forty-six tree species were identified in the bluff forest. Included in this total are fig (Ficus Carica), a fruit tree found growing near a house, tr-f-liate orange (Pancirus trifoliata), herclules club (Aralia spinosa), osage orange (Maclura pomifera), prickly ash (Zanthoxylum Clava-Herculis), redbud (Cercis canadensis), and American holly (Ilex opaca). These latter species may be considered as either s---hrubs or small trees. All specimens of these species encountered onsite were shrub size.2.2-3 GG ER Sampling indicated a density of approximately 161 trees per acre and a total basal area of about 86 square feet per acre. In the bluff forest, sweetgumx (Liquidambar Stryaciflua), water oak (Quercus nigra), southern red oak (Quercus falcata), American elm-TUlmus americana), and hTikorTes (Carya spp.) were the dominant species.These trees comprised approximately 63 percent of the total basal area and about 58 percent of the total number of trees. All of these species are commercially valuable (Ref. 3).Six species of trees observed in the bluff forest but not encountered in the sample plots were willow oak (Quercus Phellos), yellow chestnut oak (Quercus MuehlenbeFgii), slippery elm (Ulmus rubra), red maple (Acer rubrum), empress tree (Paulownia tormentosa) 3 and shortleaf pine (Pinus echinata).

These species were present in limited numbers and constituted only a minor portion of the bluff forest overstory.

2.2.2.2.2 Understory Vegetation Inventories of understory vegetation were conducted in July and August 1972 (summer season), January and February 1973 (winter season), and May 1973 (spring season) using systematic sampling methods (sampling locations are shown in Figure 2.2-1). All plants occurring in sample plots were identified to genus or species with the exception of the grasses and sedges which were identified to family. Due to flooding by the Mississippi River, the bottomlands were only partially sampled in January and February and were not sampled in May.During summer sampling, 162 plant taxa were recorded.

Of this total, 25 occurred exclusively in the bottomlands and 50 occurred exclusively in the bluffs. Only 78 taxa were recorded during winter sampling; 11 taxa occurred exclusively in the bottomlands and 22 occurred exclusively in the bluffs. In spring sampling, 148 taxa were recorded in the bluffs. The reduction of plant taxa from 162 identified in the summer sampling period to 78 identified in the winter sampling period resulted primarily from the seasonal retrogression of summer annuals and dormant perennials.

The subsequent regrowth of the perennials and the growth of spring and some summer annuals was reflected in the increase from 78 taxa identified in January and February to 148 identified in May. If flooding had not prohibited spring sampling in the bottomlands, the number of taxa recorded in the May sampling would have been greater (Ref. 4).3 This species is an ornamental tree that has been introduced from Asia and was probably planted on the site.2.2-4 GG ER Type maps of the seasonally dominant understory vegetation are presented in Figures 2.2-3 through 2.2-5.a. Bottomlands Ninety-seven plant taxa were recorded during sampling of the bottomland understory vegetation conducted in July and August 1972. The following plants were most abundant and comprised 59 percent of all understory cover: asters (Aster spp.), buckvine (Ampelopsis arborea), dewberries (Rubus spp.), grasses (Poaceae), sugarberry (Celtis laev-i-ata), poison ivy (Rhus radicans), false nettle (Boehmeria cylindrica),'Johnson grass (Sorghum halepense), trumpet creeper (Campsis radicans)and ladies eardrops (Brunnichia cirrhosa).

References 4 and 5 reported that the same taxa comprised 51 percent of all understory cover (117 taxa sampled) in the summer on a similar bottomland hardwood area (Durango Hunting Club) located adjacent to the east bank of the Missis-sippi River about 20 miles south-southwest of the Grand Gulf site.In the January and February 1973 sampling, the number of identified bottomland taxa decreased from 97 to 48.The most abundant taxa (73 percent of all understory vegetation cover) were asters, dewberries, grasses, nemophila (Nemophila microcalyx), sedges, daisy fleabane (Erigeron spp.), vetches, (Vicia spp.), violets (Viola spp.), chickweed (Stellaria spp.), and bedstraw (Galium spp.) These same taxa 4 comprised 72 percent of all understory cover occurring on Durango during the winter of 1972 (Ref. 4).Due to flooding of the bottomlands, no sampling could be conducted during the spring. However, the Durango study indicated that asters, dewberries, grasses, sugarberry, and poison ivy are the most abundant understory vege-tation occurring in the bottomlands during the spring and comprise about 33 percent of all understory cover (Ref. 4).Dewberries, asters, and grasses were dominant taxa in all seasons sampled at Grand Gulf and Durango. At Grand Gulf, these taxa comprised 26 percent of all bottom-land summer understory cover and 44 percent of all bottom-land winter understory cover. The increase in the cover of these taxa in the winter was due to a decrease in the cover of other taxa.Except nemophila and chickweed which did not occur on Durango) study plots in this season.2.2-5 GG EP Large fields and forest openings occupied approximately 10 percent of the bottomland area and supported plant taxa that ordinarily did not occur in the forested areas.Dominant field taxa in the summer (8 percent of all the bottomland understory cover) were Johnson grass, sump-weed (Iva annua), balloon vine (Cardiospermum Halicacabum), and golden rod (Solidaqo altissima).

In the winter, the dominant field taxa (6 percent of all the bottomland understory cover) were henbit (Lamium amplexicaule), cranesbill (Geranium spp.), clover (Trifolium spp.), goldenrod, and dock (Rumex crispus).b. Loessial Bluffs During July and August 1972, 114 plant taxa were recorded in the sampling of the loessial bluff understory vege-tation. The following plants were most abundant and comprised 60 percent of all understory cover: switch-cane (Arundinaria tecta)., grasses, poison ivy, Japanese honeysuckle (Lonicera japonica), winged elm (Ulmus alata), sedges, oaks (Quercus spp.) asters, rattan (Berchemia scandens), and green briars (Smilax spp.)In the January and February 1973 sampling, the number of identified bluff understory taxa decreased from 114 to 60. The most abundant taxa (70 percent of all under-story vegetation cover) were switchcane, Japanese honey-suckle, qrasses, sedges, asters, nemophila, oaks, haircap moss (Family Musci), crossvine (Bignonia capreolata), and violet (Viola spp.).In the May 1973 sampling, 148 understory taxa were recorded.

This was an increase of about 147 percent over the total number of taxa recorded in the winter (60) and a 30 percent increase over the number of taxa recorded in the summer (114). The large number of taxa recorded in the spring resulted from the presence of many short-lived spring annuals. The most abundant taxa (52 percent of all understory vegetation cover)were poison ivy, switchcane, Japanese honeysuckle, grasses, spreading bladder fern (Cystopteris fragilis), sedges, winged elm, Virginia creeper (Parthenocissus quinquefolia), rattan, and oaks.Switchcane, grasses, Japanese honeysuckle, sedges and oaks 5 were. dominant in all seasons. These taxa com-prised 42 percent of all bluff summer understory cover, Small oaks growing close to the ground were somewhat protected from wind and cold and most of their leaves stayed green during the winter.2.2-6 GG ER 51 percent of all bluff winter understory cover, and 28 percent of all bluff spring understory cover. The changes in the cover of these taxa resulted from sea-sonal retrogression and recrudescense of other plant taxa.Large field and forest openings occupied approximately 15 percent of the bluff area and supported plant taxa that ordinarily did not occur in the forested areas.Dominant field taxa in summer (3 percent of all the bluff understory cover) were goldenrod, sida (Sida rhombifolia), goatweed (Croton capitatus), mare'istail (Erigeron canadensis), butterfly pea (Centrosema virginianum), and dog-fennel (Eupatorium capillifolium).

In the winter, the dominant field taxa (4 percent of all the bluff understory cover) were clover, chickweed, dog-fennel, henbit, dock and cranesbill.

Dominant field taxa in the spring (4 percent of all the bluff understory cover) were low hop clover (Trifolium dubium), goldenrod, cranesbill, and dog-fennel.

Dog-fennel was a dominant in the field in all seasons.2.2.2.2.3 Forest Midstory Eleven ligneous or woody vines Which were common in the forest understory and midstory on the site are listed below: Buckvine (Ampelopsis arborea)Rattan (Berchemia scandens)Cross-vine (Bignonia capreolata)

Red-berried moonseed (Cocculus carolinus)

Greenbrier (Smilax spp.)Japanese honeysuckle (Lonicera japonica)Virginia creeper (Parthenocissus quinquefolia)

Kudzu (Pueraria lobata Poison ivy (Rhus radicans)Wild grape (Vitis spp.)With the exception of.Kudzu, which grows exclusively in the bluffs, all of these taxa occurred in both the bottomlands and the bluffs.Samplina and field observations indicated that buckvine, red-berried moonseed, trumpet creeper, and Virginia creeper were more abundant in the bottomlands; cross-vine, Japanese honeysuckle, poison ivy and rattan were more abundant in the bluffs; and greenbrier and wild grape were equally abundant in the bluffs and bottomlands.

Kudzu is a perennial vine that was introduced into Mississippi from Asia to assist in controlling erosion. It has stems up to.60 feet long and frequently chokes out young forest trees. On site, it was most abundant on severely eroded bluffs and along roadsides; it had probably been planted in these locations to control erosion.2.2-7 GG ER Two additional plant taxa commonly occurring in the bottomland and bluff forest midstory were Spanish moss (Tillandsia usneoides) and American mistletoe (Phoradendron flavescens).

Spanish moss is an epiphyte 6 which clings to the branches of trees. American mistletoe is a parasite that grows on trees and absorbs water and minerals directly from its host. Although it is epiphytic, Spanish moss occasionally causes damage to supporting trees because it may become saturated with rain water during severe storms and cause branches to break. Field observations indicated that Spanish moss and American mistletoe were most abundant in the bluff forest.2.2.2.3 Birds Field observations using several different systematic methods were employed to inventory birds on the site. A monthly census of birds was made from observation stations established on Hamilton and Gin Lakes, at the Grand Gulf Military Park observation tower, and on the east bank of the Mississippi River. Bimonthly censuses were conducted in 40-acre plots located in the bluff and bottomland forest communities.

Birds occurring along two 300-foot-wide belt transects which traversed all habitats on the site, and along approximately 16,100 feet of field edge in both the bottomlands (8000 feet) and bluffs (8100 feet) were also censused bimonthly.

Census locations are shown in Figure 2.2-6.One hundred and forty avian species have been,observed on.:or near the GCrand Gulf.:.:site.

Review :of range maps:presented in. Reference'6 indicated that, with the exception of ....,wo :species,, the white ibis (Eudo0cimus

ý.albus) and'Louisiana heron (Hydrannassa tricolor)-, all observed.

species regularly occur in the'area.

On the basis of seasonal occurrence information

presented.

in 'Reference 6, of the 140 species recorded 44 (31 percent) are permanent residents in the area; 44 (31 percent) are resident only during the spring and summer: 20 (14 percent) occur only during spring and fall migration; and 32 (23 percent) are resident in the area only during the winter.None of the observed species have been designated as endangered or threatened by the U. S. Fish and Wildlife Service (Ref. 7).However, 15 of the observed species have been declining in numbers and concern has been expressed about the future of these species (Ref. 8). These species are listed below: White ibis (Eudocimus albus)Sharp-shinned hawk (Accipiter striatus)Red-shouldered hawk (Buteo lineatus)Marsh hawk (Circus cyaneus)Osprey (Pandion haliaetus)

American kestrel (Falco sparverius Yellow-billed cuckoo (CZoccyzus americanus)

Barn owl (Tyto alba)6 AAn epiphyte is a plant that derives its moisture and nutrients from the air and rain and usually grows on another plant.2.2-8 G.G ER Common nighthawk (Chordeiles minor)) Red-headed woodpecker (Melanerpes erythrocephalus)

Hairy woodpecker (Dendrocopus villosus)Purple martin (Progne subis)Loggerhead shrike (Lanius ludovicianus)

Yellow warbler (Dendroica petechia)Yellow breasted chat (Icteria virens)2.2.2.3.1 Avian Fauna of the Forest Communities Censuses 7 indicated that the cardinal (Cardinalis cardinlis), Carolina wren (Thryothorus ludovicianus), Carolina chickadee (Parus carolinensis), blue jay (Cyanocitta cristata), rufous-sided towhee (Piplio erythropthalmus), .and red-bellied woodpecker (Centurus carolinus) were common8, permanent residents in both the loessial bluff and bottomland forest communities.

One permanent resident, the tufted titmouse (Parus bicolor), was common only in the loessial bluff forest. The brown thrasher (Taxostoma rufum), another permanent resident, was common only between October and April when large numbers evidently wintered on the site.Common winter residents on the site were the white-throated sparrow (Zonotricia albicollis), robin (Turdus migratorius), yellow-shafted flicker (Colaptes auratus), ruby-crowned kinglet (Regulus calendula), myrtle warbler (Den ia coronata), and yellow-bellied sapsucker (Sphyrapicus varius). All of these species were common in both the loessial bluff and bottomland forest communities.

The myrtle warbler, however, was much more numerous in the bottomland forest.Common summer residents on the site were the white-eyed vireo (Vireo griseus), red-eyed vireo (Vireo olivaceus), parula warbler (Pa-rula americana), hooded warble!r(Wilsonia citrina), prothonotary warbler (Protonotaria citrea), worm-eating warbler (Helmitheros vermivorus), Acadian flycatcher (Empidonax virescens), indigo bunting (Passerina cyanea), and yellow-billed cuckoo (Coccyzus americanus).

The red-eyed vireo, parula warbler and worm-eating warbler primarily inhabited the loessial bluff forest; the prothonotary warbler, white-eyed vireo, hooded warbler, Acadian flycatcher, and yellow-billed cuckoo were abundant in both the bottomland and loessial bluff forest.The cardinal, blue jay, rufous-sided towhee, and white-throated sparrow subsist largely on seeds and fruits; the robin, brown thrasher, red-bellied woodpecker, yellow-bellied sapsucker, and Carolina chickadee are normally omnivorous; and the vireos, warblers, yellow-billed cuckoo, tufted titmouse, and Acadian flycatcher are primarily insectivorous.

7 Census, as used in this report, refers only to a count or talley of birds observed and does not imply that all individuals pre-sent were recorded.8) Common is defined herein as more than ten individuals per 100-acres.

2.2-9 GG ER 2.2.2.3.2.

Avian Fauna of the Field-Forest Ecotone Avian species occurring within 50 feet of the edge of a field were considered to inhabit the field-forest ecotone. Species primarily inhabiting the field edge, that were permanent residents on the site, included the mourning dove (Zenaidura macroura), bobwhite (Colinus virginianus), red-winged blackbird (Agelaius phoeniceus), mocking-bird (Mimus polyglottos), and loggerhead shrike (Lanius ludovicianus).

Mourning doves were most numerous during the winter months when as many as 100 to 200 were observed feeding on the seeds of a variety of weed species growing along roadsides and in old fields.Bobwhite, loggerhead shrikes, and mockingbirds are most numerous in areas that are predominantly fields with scattered woodlots.Since the Grand Gulf site is mostly wooded, these species were present in limited numbers. The red-winged blackbird commonly occurred along field edges throughout-the year.Field-edge species resident on the site only during the winter included the white-throated sparrow, fox sparrow, (Passerella iliaca), lark sparrow (Chondestes grammacus), and field sparrow (Spizella pusilla).

Of these species, the white-throated sparrow was the most abundant with an average of 10.7 birds occurring along every 100 feet of field edge in the December 1972 census.Species resident in the field edge only during the summer included the indigo bunting, painted bunting (Passerine ciris), yellow-breasted chat (Icteria virens), yellowthroat (Geothlypis thrichas), rough-winged swallow (Stelgidopteryx ruficollis), and orchard oriole (Icterus spurius).

Only the indigo bunting and yellow-breasted chat occurred commonly.

Occasionally, 200 to 300 rough-winged swallows were observed perched on powerlines traversing fields adjacent to Hamilton and Gin Lakes.During migration, the brown-headed cowbird (Molothrus ater) and American goldfinch (Spinus tristis) were particularly abundant along field edges. With the exception of the rough-winged swallow, field-edge species largely subsist on plant seeds.2.2.2.3.3 Avian Fauna of Hamilton and Gin Lakes The following species of water-dependent birds were observed on Hamilton and/or Gin Lakes: Water Birds Anhinga (Anhinga anhinga)Great blue heron (Ardea herodias)Little blue heron (YTFlTda caerulea)Green heron (Butorides virescens)

Louisiana heron (Hydranassa tricolor)Cattle egret (Bubulcus ibis)Common egret (Casmerodius albus)2.2-10 GG ER White ibis (Eudocimus albus)Wood ibis (Mycteria aierciana)

American coot (Fulica americana)

Pied-billed grebe (Podilymbus podiceps)Belted kingfisher (Megaceryle alcyon)Waterfowl Wood duck (Aix sponsa)Mallard (Anas platyrhynchos)

Canvasback (Aythya valisineria)

Gadwall (Anas strepera)Pintail (Anas acuta)Blue-winged teal (Anas discors)Green-winged teal (Anas carolinensis)

Of these species, only the wood duck, great blue heron, and belted kingfisher are permanent residents in this section of Mississippi.

With the exception of the American coot and the pied-billed grebe, the remaining species of water birds are primarily summer residents.

The American coot, the pied-billed grebe and the remaining species of waterfowl occur in the area only during the fall, winter, and early spring. The water birds are carnivorous, normally feeding on a variety of fish, reptiles and amphibians whereas the waterfowl are omnivorous, subsisting on a variety of aquatic invertebrates and seeds and leaves of aquatic and terrestrial plants.Utilization of the lakes by water-dependent species was seasonal.During the summer and early fall of 1972 and late spring of 1973, fewer than ten individuals of any single species were concurrently observed on the lakes. During the summer of 1973, however, about 300 little blue herons and about 100 cattle egrets and common egrets were observed at dusk flying over the lakes in a southerly direction.

The herons and egrets were evidently flying to a roosting area located south of the site near Bayou Pierre. Most of these birds came from areas north of the site and only a small number (generally less than 10) were observed on Hamilton and Gin Lakes at the same time.Lack of utilization of the lakes by water-dependent birds during the summer was not unusual since, with the exception of anhinga, kingfisher and wood duck, the habitat requirements of all water-dependent birds observed at Grand Gulf during the summer are more readily fulfilled by shallow marshes andponds (water depth less than two feet) than by lakes.The wood duck is a common permanent resident of the oxbow lakes occurring along the Mississippi River bottomlands.

It nests in tree cavities and raises its young in brush-covered portions of the oxbow lakes. Since the bottomlands of the Grand Gulf site contained these basic elements (trees with cavities and oxbow 2.2-11 GG ER lakes), special efforts were devoted to evaluating the importance of the lakes to wood duck production by using observational and trapping techniques in 1972 and 1973. Only one brood of wood ducks was observed on the lakes-during the entire summer of 1972 and none were seen during the spring and summer of 1973. No wood ducks were captured in baited floating traps placed- in brush-covered sections of the lakes during August and September 1972.The apparent lack of utilization of the lakes by-wood ducks during the summer period can probably be attributed to the scarcity of submerged or emergent aquatic vascular plants, except for the duckweed species Lemna minor and Spirodela polyrhiza.

Wood duck utilization of the lakes increased noticeably in October 1972 when approximately 200 wood ducks roosted each evening in the north end of Gin Lake. In November, at the height of fall migration, the estimated number of roosting wood ducks increased to over 600. From late December 1972 through February 1973, the number of wood ducks estimated to be using Hamilton and Gin Lakes fluctuated between 50 and 300.. This fluctuation in wood duck numbers is probably attributable to the creation of additional roosting and feeding habitat in nearby areas as a result of flooding of bottom-land areas by the Mississippi River.Beginning in late November and continuing through February, periodic concentrations of several hundred to several thousand mallards and a few gadwall and green-winged teal were observed feeding in flooded soybean fields adjacent to the northern boundary of the Grand Gulf site. After feeding, many of these ducks utilized flooded areas on and near the site for resting.During the winter of 1972-73 a few American coot (estimated to number less than 10) wintered on Hamilton and Gin Lakes. During the preconstruction study period, most wintering waterfowl left.the Grand Gulf area by mid-March, at which time the surmmer-resi-dent herons and egrets began to return. Migrating blue-winged teal were periodically noted feeding in flooded fields adjacent to Hamilton and Gin Lakes during the latter part of March and April 1973. By May 1973 all wintering and migrating water-dependent species had departed from the area and all summer-resident species had returned.Nest searches were conducted during March, May and June 1973 to determine if any heron, egret or anhinga rookeries existed on the site and to survey the extent of onsite wood duck nesting. No rookeries were found and only one wood duck nest was located on March 28. This wood duck nest was subsequently inundated by the rising waters of the flooding Mississippi River.Two additional species, the prothonotary warbler and the rough-winged swallow, commonly occur in the vicinity of the lakes during the summer. The prothonotary warbler also nests in tree cavities.During May, five prothonotary warbler nests were found in cavities 2.2-12 GG ER of willow trees growing near Hamilton and Gin Lakes. The rough-) winged swallow is an adaptable species that will use any type of cavity for nesting; however, it prefers to nest in burrows which it excavates in steep river banks. In the Grand Gulf area, rough-winged swallow nests were often located in the cut sides of steep bluff slopes that resulted from the construction of local roads.Insects in the vicinity of the lakes provided food for the insectiv-orous swallows and prothonotary warbler. Both species winter in Central America and occur on the site only during the spring and summer.2.2.2.3.4 Vultures, Hawks and Falcons The following species were observed on the site: Black vulture (Coragyps atratus)Turkey vulture (Carthartes aura)Red-tailed hawk (Buteo jamaicensis)

Red-shouldered hawk (Buteo lineatus)Broad-winged hawk (Buteo platypterus)

American kestrel (Falco sparverius)

Marsh hawk (Circus cyaneus)Sharp-shinned hawk (Accipiter striatus)Mississippi kite (Ictinia misisippiensis)

Black and turkey vultures were permanent residents on the site.The black vulture was more abundant than was the turkey vulture.Very few turkey vultures were observed during the winter months.Both species are carrion eaters and were often seen scavenging along roadsides.

The largest number of vultures seen on the site was on July 5, 1973 when 25 black and 5 turkey vultures were at-tracted to the Gin Lake boat landing by fish remains left by fisher-men. A similar concentration of vultures occurred on January 16, 1973, at the end of the deer season, when 25 black vultures and 1 turkey vulture were attracted to deer remains left at the Mississippi-Arkansas Hunting Camp located on the Grand Gulf site.On April 30, a black vulture was flushed from its nest in the loessial bluff forest at the interface of the bluffs and bottom-lands. The nest, which was just a depression on the ground, was subsequently flooded and abandoned.

The red-tailed hawk and red-shouldered hawk were permanent residents on the site; the broad-winged hawk was resident on the site only during the summer; and the marsh hawk, American kestrel and sharp-shinned hawk occurred on the site only during migration.

The broad-winged hawk and red-tailed hawk were the most abundant of the hawks. With the exception of the marsh hawk (an inhabitant of grasslands and marshes), woodlands and wooded margins are the pre-ferred habitat for all the hawks observed.

Hawks are carnivorous and feed on a variety of small mammals, other birds, and occasion-ally reptiles and amphibians.

2.2-13 GG ER The Mississippi kite was abundant in the Grand Gulf area and was observed on the site from April until September.

Kites subsist almost entirely on insects: during July 1972, as many as 35 indi-viduals were observed soaring over the fields on the site consuming insects. The largest breeding populations of the Mississippi kite in the United States occur along the Lower Mississippi River valley;the kite nests in tall trees, particularly cottonwood, growing along stream bottoms. No Mississippi kite nests were found on the site although potential nesting habitats were thoroughly searched in May and June of 1973. The migration habits of the Mississippi kite are not well defined; however, it is believed to winter in southern Texas and Mexico (Ref. 9). Most Mis-sissippi kites were gone from the Grand Gulf area by the end of August, presumably migrating to their wintering grounds.On May 11, 1973, an osprey was observed on the western (Louisiana) bank of the Mississippi River about 2 miles southwest of the site.This individual was probably migrating north. This was the only osprey observed in the area during the study period from June 1972 through August 1973.2.2.2.3.5 Owls During the preconstruction study period, great horned (Bubo virginianus), screech (Otus asio), barn (Tyto alba), and barred owls (Strix varia) were observed on or near the site. All of these species are permanent residents in this section of Missis-sippi (Ref. 6).A pair of great horned owls were present on Middle Ground Island from the summer of 1972 until the island was inundated in April 1973. The ready availability of a source of food provided by the thousands of blackbirds that roosted on the island may have attracted the owls to the island.The occurrence of screech owls on the site was sporadic.

The species was recorded in September, October, November and December 1972 and July 1973. The screech owl generally inhabits orchards and small woodlots rather than heavily wooded areas such as those occurring on most of the Grand Gulf site. The largest number of screech owls noted on the site was three in September 1972.A single barn owl was observed on the site in July 1973. This species hunts mice and rats in marshes and fields; it nests in barns, abandoned buildings and tree cavities.The barred owl was abundant on the site. A spring census of owl calls indicated that approximately six barred owls were present in the bluff forest on the site and an additional seven inhabited woodlands adjacent to the site. Additional barred owls were present in the bottomland forest; because of flooding, however, the bottomlands could not be censused.2.2-14 GG ER Owls are carnivorous, feeding largely on small mammals. Normally owls are nocturnal, inhabiting secluded woodlands during the day and hunting along forest edges and fields at night.2.2.2.3.6 Blackbirds A blackbird roost was located on Middle Ground Island in the Mississippi River just northwest of the site. Blackbirds left the roost at dawn and flew to Mississippi and Louisiana to feed, returning to the island at dusk. The majority of the birds using the roost were common grackles (Quiscalus quiscula), although starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus) also used it. Most of the blackbirds flew over the Grand Gulf site to agricultural areas which provided an abundance of food (seeds and insects).

When the mast crop matured during the latter part of September, however, large numbers of blackbirds were observed feeding in oak trees on the site.Monthly estimates of the number of birds leaving the roost and flying to the Mississippi 9 side of the river indicated that the number of roosting birds declined about 85 percent between August.(90,000 birds) and October (14,000 birds) of 1972. As fall pro-gressed in 1972, however, the number of blackbirds using the roost increased tremendously until a peak was reached in December 1972 when an estimated 500,000 birds were observed flying from the island to Mississippi.

The January and February 1973 estimates showed a decrease to a wintering population of approximately 250,000 birds.March 1973 estimates indicated a further decrease to 123,000 birds.The island was inundated during April, May and most of June 1973 and only the top 15 to 20 feet of trees growing on the island was available to the roosting blackbirds.

Consequently, the blackbird counts dropped sharply to 2000 to 3000. By July 1973, the flood-waters had receded and the estimated number of blackbirds leaving the island increased to 10,000.2.2.2.3.7 Upland Game Birds Species of upland game birds occurring on the site were woodcock (Philohela minor), mourning dove (Zenaidura macroura), bobwhite (Colinus virginianus), and wild turkey (Meleagris gallopavo).

The woodcock is a migratory species, breeding in the northeastern and north central United States and Canada and wintering primarily in Louisiana (Ref. 10). Woodcock are crepuscular, resting in pro-tective woodlands during the day and flying at twilight to fields to feed on earthworms and other soil invertebrates.

Spotlight surveys of fields indicated that only a few woodcock were wintering on the site in 1972-73. The maximum number of woodcock counted during any survey was seven.9 Estimates were not made of the number of blackbirds flying to Louisiana.

2.2-15 GG ER The mourning dove, bobwhite, and wild turkey were all permanent residents on the site; the mourning dove was also the most abundant of the upland game species. During preconstruction studies, it reached its highest numbers in December 1972 when up to 200 doves were frequently observed feeding on seeds of weeds in the bottom-land fields.During 1972-73 only a few bobwhite (estimated to number less than 100) were present on the largely wooded Grand Gulf site. Bobwhite become most abundant in agricultural areas containing an inter-spersion of fields and small woodlots.

This species is omnivorous, feeding on seeds, fruits, plant buds, and insects.Although the Grand Gulf site contained suitable wild turkey habitat (hardwood forest), only two wild turkeys were observed on the site.Both turkeys were seen during the spring of 1973 and may have been displaced by flooding of the Big Black River bottomlands (north of the site) which are reported to support a sizeable turkey population (Ref. 11). The wild turkey inhabits mature forests and is omnivorous, consuming seeds, mast, fruits, plant buds, and insects.In recent years, the range and numbers of this species have been increasing throughout Mississippi, including Claiborne County (Ref. 11). There was no known upland game bird hunting con-ducted on the site during the 1972 hunting season. Si'nce the site did not support a sizeable upland game bird population, hunting of upland game birds was not a significant recreational activity on the site.2.2.2.4 Mammals Field data on mammals were gathered by direct field observations, hunter bag checks, trapping, censusing squirrel nests, nightlight counts, and tallying road kills. The location of mammalian sampling plots and nightlighting routes are shown in Figure 2.2-7.Thirty-three mammalian species were observed on the Grand Gulf site.None of the observed mammals have been designated as endangered or threatened by the U.S'. Fish and Wildlife Service (Ref. 7). How-ever, black bear (Ursus americanus), a species listed as threatened by both the Mississippi came and Fish Commission (Ref. 12) and the Mississippi Natural Heritage Program (Ref. 13), have been seen on the site four times since February 1977. In addition, bear tracks and other sign have been observed in the bottomlands just south of the Grand Gulf property line. This species is discussed further in Section 2.2.2.7.A cougar (Felis concolor), was observed crossing Grand Gulf road near the northeast corner of the site on June 17, 1973. According to Reference 14, there are no authenticated records 1 0 of cougar occurring in Mississippi during this century. However, reports 10 An authenticated record normally requires the collection of the animal for verification of identification by a mammalian taxonomist.

2.2-16 GG ER of cougar sightings, particularly from the Pascagoula Swamp region of George and Jackson counties (in southeastern Mississippi), occur periodically.

No other cougar sightings were made in the Grand Gulf area, nor was any cougar sign, such as tracks or scats, encountered during the preconstruction studies. The cougar may have been temporarily displaced from a remote section of the Mississippi River bottomlands by the 1973 spring flood. No sightings have been reported in the Grand Gulf area since 1973.At least 25 free-ranging dogs were present in the Grand Gulf area during preconstruction studies and were occasionally observed chasing deer. However, no deer are known to have been killed by these dogs.2.2.2.4.1 Small Mammals Small mammals, as identified in this report, include mice, shrews, moles, voles and rats. Some small mammal species are herbivores, subsisting entirely on plants; others are insectivores, subsisting largely on invertebrates; and others are omnivores, consuming both plant and animal matter. Small mammals are a major source of food for larger carnivorous animals such as owls, hawks, foxes and snakes.They are an important pathway for energy flow through terrestrial ecosystems, with the population density of larger carnivorous species often fluctuating with density fluctuations of small mammal popula-tions. These variations can result from environmental factors such as food, weather, and cover which influence mortality, natality, emigration, and immigration of population (Ref 15). The existence and abundance of animal species in any locality is also dependent on environmental changes wrought by man. Population densities of these small mammals inhabiting fields or open areas in forested regions are highly dependent upon land use practices of man.Populations generally reach highest densities in recently abandoned or unused fields. In the south, small mammal populations normally reach highest densities in the fall or winter (Ref. 16).The habitat preferences, ecological distribution, and species composition of small mammals on the Grand Gulf site were deter-mined by saturation trapping in the following habitats: Grand Gulf Island forest Bottomland forest (east of Hamilton Lake)Bottomland fields Loessial bluff forest Loessial bluff fields Trapping was conducted in the various habitats11 during the fall (October and November 1972), winter (January and February 1973), Due to flooding, Grand Gulf Island was not trapped in the winter and spring; the bottomland forest and fields were not trapped in the spring.2.2-17 GG ER spring (May and June 1973) and summer (July and August 1973). The following 10 small mammal species were collected during these trapping periods: White-footed mouse (Peromyscus leucopus)Cotton mouse (Peromyscus gossypinus)

House mouse (Mus musculus)Fulvous harvest mouse (RT--ethrodontomys fulvescens)

Golden mouse (Ochrotomys noutalli)Pine vole (Pityms pinetorium)

Shorttail shrew (Blarina brevicauda)

Least shrew (Cryptotis parva)Hispid cotton rat (Sigmodon hispidus)Rice rat (Oryzomys palustris)

Three additional small mammal species occurring on the site but not collected in traps were the eastern mole (Scalopus aquaticus), eastern woodrat (Neotoma floridana) and Norway rat (Rattus norvegicus).

1 2 The eastern mole is a tunneling mammal whose residence on the site was indicated by the presence of raised tunnels of earth in pastures and fields. The presence of woodrats was indicated by large stick and leaf nests located in wooded por-tions of the site that supported a dense understory growth. One Norway rat was collected in a hunting camp.The shorttail shrew, cotton mouse, golden mouse, and white-footed mouse inhabited wooded areas; whereas, the hispid cotton rat, rice rat, house mouse, fulvous harvest mouse, pine vole, and least shrew inhabited fields or large openings within the forest. All of the species collected were expected to inhabit the site and, based on information presented in Reference 14, were a typical representation of the species composition of small mammals occur-ring in similar habitats of southwest Mississippi.

The number of small mammals collected varied considerably among seasons. This variation was expected inasmuch as considerable seasonal and yearly variation typically occurs in small mammal populations (Ref. 16). The number of small mammals collected in the bluff forest-was 7 in the fall, 3 in the winter, 18 in the spring, andl10 in the summer. In the bottomland forest, 6 small mammals were collected in the fall, 10 in the winter, and 1 in the summer. In the loessial bluff fields, 20 small mammals were collected in the fall, 15 in the winter, 2 in the spring, and 5 in the summer. In the bottomland fields, .52 were collected in the fall, 19 in the winter, and 12 in the summer.A reduction in small mammal densities occurred between fall and winter in all habitats except in the bottomland forest east of 12 The special museum traps used to collect small mammals were not capable of capturing the relatively large woodrat. The eastern mole seldom occurs on the ground surface and the Norway rat is chiefly an inhabitant of buildings and dumps.2.2-18 GG ER Hamilton Lake where an increase occurred.

The increase of small mammals in the bottomland forest could have resulted from a con-centration of individuals displaced by inundation of the bottom-land forest adjacent to the area sampled. The large number of small mammals collected in the bottomland fields during fall trapping is probably attributable to the following factors: a. The loessial bluff fields had been grazed by cattle during the spring of 1972, and therefore, did not support as dense a growth of vegetation as did the bottomland fields. This thicker growth created more cover in the bottomland fields, thus resulting in better habitat for field-dwelling small mammals.b. Of the 30 hispid cotton rats collected in the bottom-land fields, 22 were juveniles, indicating that trapping probably occurred during a period of dispersal of juvenile hispid cotton rats.The 1973 spring trapping, which could only be conducted in the bluffs because the Mississippi River had flooded the bottomlands, indicated that the number of small mammals in the loessial bluff forest habitat had increased over the number present during the winter; the number in the bluff field habitat, however, had decreased.

During summer trapping, the opposite trend occurred; the number of small mammals decreased in the forest habitat and increased in the field habitat.-) The results of trapping in the field habitat during both spring and summer periods, however,.are probably not a true indication of small mammalnumbers in the loessial bluff fields because ants stripped the bait off most of the traps.In an effort to evaluate the potential large-scale migration of small mammals from the bottomlands to the bluffs because of the extensive bottomland flooding, some limited small mammal trapping was conducted at the interface of the loessial bluffs with the bottomlands during the periods April 10 through 13 and May 15 through 18, 1973. During these two trapping periods, six small mammals were captured in two quarter-acre sample plots located in forest habitat and nine small mammals were captured in one quarter-acre sample plot located in field habitat. Compared to the results of previous trapping, these data do not indicate that large number of small mammals migrated from the bottomlands to the adjacent bluffs as the floodwaters rose. When the floodwaters receded in June, selective small mammal trapping was conducted in order to evaluate the repopulation of the bottomlands by small mammals.Trapping results indicated that house mice were quickly repopulating the fields as the floodwaters receded. Between June 21 and July 10, 13 house mice, 2 hispid cotton rats, and I white-footed mouse were captured in the bottomland fields. The sparsity of the ground cover may account for the capture of only two hispid cotton rats and no fulvous harvest mice or least shrews, species which were 2.2-19 GG ER previously collected in the fields during fall and winter trappings.

The most significant information obtained from these data is the following:

although the bottomland fields had been completely inundated from late March through late June 1973, some small mammal: species repopulated the field habitats almost immediately after the floodwaters receded.Similar trapping was conducted in the bottomland forest east of Hamilton Lake from June 26 through July 23 and in the Grand Gulf Island forest from July 11 through July 23, 1973. Only three small mammals (one house mouse, one cotton mouse, and one shorttail shrew)were captured in the forest east of Hamilton Lake and none were captured in the Grand Gulf Island forest. These trapping data in-dicate that the rate of repopulation of the bottomland forests by small mammals was much less than that of the bottomland fields. The regrowth of ground cover in the forest proceeded at a slower rate than it did in the fields. The greater sparsity of ground cover in the forest may account for the apparent slowness of small mammals to repopulate the forest habitat. These trapping data also suggest that very few, if any, small mammals of the bottomland forest were able to survive the duration of the flood by living in trees. The cotton mouse and golden mouse, two species inhabiting the bottomland forest prior to the flood, are partially arborial and could have been expected to survive in trees for the duration of the flood provided they could obtain sufficient food to sustain themselves.

A paper providing an in-depth analysis of the effect of the flooding on the small mammal population has been published by the Mississippi Academy of Science (Ref. 17).Scheduled small mammal trapping in the bottomlands was resumed in the summer season (August 1 through 8, 1973). Twelve small mammals (five species) were captured in the field habitat, one was captured in the forest habitat west of Hamilton Lake, and none were captured in the Grand Gulf Island forest. During winter trapping, 19 small mammals were captured in the bottomland fields and 10 were captured in the bottomland forest east of Hamilton Lake. The summer trapping data indicate that small mammal popu-lations in the bottomland fields were recovering from the effects of the prolonged flood; whereas, the small mammal populations in the bottomland forest habitats apparently were not.The probability of capturing small mammals did not remain constant during the sampling periods because heavy rainfall tripped the traps on several occasions.

Consequently, no valid estimate of small mammal population density can be calculated on a per-acre-basis. The data do indicate, however, the relative abundance of small mammals inhabiting the various habitats on the site and can serve as an index of abundance for future sampling.2.2.2.4.2 Larger Mammals In comparison to small mammals, the larger mammals are generally more difficult to inventory.

Attempts to determine the relative 2.2-20 GG ER abundance of the larger mammals inhabiting the Grand Gulf site were only partially successful even though a variety of techniques were employed.

Direct field observations, line trapping, hunter bag checks, nightlight counts, and a tally of road kills indicated that the following species of larger mammals commonly occurred in the Grand Gulf area: Eastern chipmunk (Tamias striatus)Gray squirrel (Sciurus carolinensis)

Fox squirrel (Tciurus niger)Cottontail rabbit (Sylvilagus floridanus)

Swamp rabbit (Sylvilagus aquaticus)

Beaver (Castor canadensis)

Raccoon (Procyon lotor)Oppossum (Didelphis marsupialis)

Armadillo (Dasypus novemcinctus)

Striped skunk (eTphitis mephitis)Gray fox (Urocyon cinereoargenteus)

Red fox (Vulpes fulva)Bobcat (Lynx rufus)Whitetail deer (OdocoTleus virginianus)

Censuses of squirrel nests occurring along vegetation transects (see Figure 2.2-1) were conducted in the bottomland and loessial bluff forests. In the fall of 1972, mean nest density (standard deviation) per 100 acres varied from 189. (40) in the bottomland forest to 218 (62) in the loessial bluff forest. Reference 18 reported a ratio of 1.09, 1.09 and 1.10 nests per squirrel over the course of a three-year study conducted in a hardwood forest in West Virginia.

Assuming a similar situation existed at Grand Gulf, there were approximately 170 squirrels per 100 acres in the bottomland forest and 200 squirrels per 100 acres in the loessial bluff forest prior to the 1972 hunting season.A systematic survey of the backwaters of Hamilton and Gin Lakes indicated that three active beaver lodges were present on the site in 1972 (Figure 2.2-7). On the basis of Reference 19 determina-tion of 5.1 beavers per lodge, approximately 15 to 20 beaver were living in Hamilton and Gin Lakes. Beaver are considered "pests" in Mississippi and a bounty is offered for killing them. During the course of the field studies, three beaver were know to have been shot by private citizens.Attempts to determine the density of rabbits and opossums on the site using live trapping were unsuccessful.

No rabbits and only eight opossums were captured.

All opossums were ear tagged and released; no marked opossums, however, were recaptured in sub-sequent trapping.1 3 The lack of trapping success was attributed to the availability of natural foods which made it difficult to 13 All opossums were captured in February 1973 in a 33-acre sample plot established in the bottomland forest. This area was sub-sequently flooded by the Mississippi River.2.2-21 GG ER lure rabbits and opossums into the baited traps. Hunter bag checks did not provide sufficient data to indicate rabbit densi-ties.1 4 Nightlight counts also failed to provide sufficient data to estimate rabbit densities.

Attempts to census predatory mammals were based on the use of tape-recorded prey calls to attract the predators..

During a three-month period from September through November 1972, the prey calls were played periodically at night from blinds and tree stands located in fields and large forest openings in the loessial bluffs and bottomlands.

Although sign and field observations indicated the presence of predatory mammals, none were attracted by the calls.Since the technique did not prove effective in counting predatory mammals, the program was discontinued.

A nightlight census was conducted on a biweekly basis to count nocturnal mammals. This technique did not provide sufficient information to develop an index of species abundance.

It did, however, serve to document the presence of several species on the site.Hunter bag checks for small game were conducted for five consec-utive weekends beginning the weekend of October 14-15, when the 1972 squirrel season opened, and continuing through the weekend of November 11-12, 1972. When the 1972-73 deer season (gun) opened on November 18, hunters in the Grand Gulf area ceased active hunting of small game. During the period that the game bags were checked, the mean hunting effort was 25.4 man-days per weekend with a range of 46 man-days on October 14-15 to 12 man-days on October 28-29 and November 11-12.Bag checks indicated that squirrels were the only small game actively hunted in the Grand Gulf area. Of 277 squirrels counted in the hunter bags, 164 (59 percent) were gray squirrels and 113 (41 percent) were fox.squirrels.

Three of the grey squirrels examined were of the uncommon melanistic (black) color phase.Most of the gray squirrels were harvested in the loessial bluff forest, while most of the fox squirrels were harvested in the bottomland forest or near field edges. Generally, the gray squirrel inhabits wooded areas with heavy understory; the fox squirrel, however, inhabits small woodlots and wooded areas with light under-story growth (Ref. 20).The whitetail deer was the largest mammal and most heavily hunted game animal occurring on the Grand Gulf site. Field observations and nightlight counts indicated that deer regularly moved back and forth between the loessial bluff and bottomland forests. During the 1973 spring flood, deer were forced from the bottomlands into the loessial bluffs. The displacement of deer from the bottomlands Only four rabbits were recorded in weekend bag checks conducted from October 14 to November 12, 1972.2.2-22 GG ER did not appear to cause an overbrowsing of the loessial bluff understory vegetation.

Field observations indicated that deer were numerous on the site. Insufficient data were obtained to accurately estimate their density; however, review of the litera-ture indicates that bottomland hardwood forests of the lower Mis-sissippi Valley typically support a carrying capacity of one deer per 10 to 12 acres and upland (bluff) hardwood forests typically support one deer per 18 to 20 acres (Ref. 21).During the 1972-73 hunting season, approximately 200 individuals hunted in the Grand Gulf area and killed an estimated 100 deer.Eighty-seven deer were examined and the age and sex recorded at four hunting camps on or adjacent to the Grand Gulf site. All deer examined appeared to be in excellent physical condition.

Antlered deer (bucks) could be legally shot on 29 days, whereas antlerless deer (does and fawns) could be legally shot only on 5 days. Of the deer examined, 94 percent of the males and 91 percent of the females were 2.5 years old or less. These age data indicate that there is heavy hunting pressure exerted on the deer population in the vicinity of the site and most deer are being shot within three years of birth. According to Mississippi Game and Fish Commission game biologist Mr. Wendell Neal (Ref. 22), hunting pressure of this nature is not unusual in areas adjacent to the Mississippi River and the deer population is generally able to sustain the heavy annual harvest.Deer hunting has not been permitted on the site since the begin-ning of construction in 1974. Hunting pressure, however, has remained heavy in the areas adjacent to the site. Deer kill data for Claiborne County compiled by the Mississippi Game and Fish Commission indicate that the deer harvest in the county has ranged from 1076 to 2034 between the 1972-73 and 1976-77 hunting seasons.Specifically, the total deer kill in the county each hunting season was as follows: Year Number 1972-73 1550 1973-74 1076 1974-75 1080 1975-76 1655 1976-77 2034 Deer are herbivorous and obtain their food by browsing on vegeta-tion growing within 6 feet of the ground. The species composition of vegetation growing in an area varies seasonally (see sub-section 2.2.2.2);

consequently, the types and amounts of vegeta-tion consumed by deer also vary seasonally.

An intensive study of the food habits of deer inhabiting a bottomland hardwood)2.2-23 GG ER forest about 20 miles south-southwest of the Grand Gulf site was conducted by Murphy (Ref. 23). Some pertinent results of Murphy's studyl5 which illustrate the seasonality of deer food habits are described below: a. Summer Aster, buckvine, dewberry, grass, sugarberry, poison ivy, and trumpet creeper comprised 46 percent of all available food plants and constituted 68 percent of all food plants consumed by deer. These species comprised 48 percent of all forage available in the Grand Gulf bottomlands.

Aster and trumpet creeper were the most important summer food plants; they comprised 48 percent of all forage consumed.b. Winter Aster, dewberry, grass, sedge, daisy fleabane, vetch, and violet comprised 69 percent of all food plants available and constituted 97 percent of all food plants consumed by deer. These species comprised 61 percent of all forage available in the Grand Gulf bottomlands.

Dewberry was the most important winter food plant; it comprised 86 percent of all forage consumed.c. Spring Aster, dewberry, sugarberry, poison ivy, and grass comprised 43 percent of all food plants available and constituted 68 percent of all food plants consumed by deer. Due to flooding, the Grand Gulf bottomlands could not be sampled during the spring. Aster and dewberry were the most important spring food plants;they comprised 60 percent of all forage consumed.2.2.2.5 Reptiles and Amphibians Information on reptiles and amphibians was compiled by tallying road kills, periodic field collection, and sampling in conjunction with fish sampling.Thirty-four reptilian species and 14 amphibian species were col-lected or observed on the Grand Gulf site in 1972-73. With the exception of the American alligator (Alligator mississipiensis), none of the reptiles or amphibians occurring in the Grand Gulf area have been designated as rare and endangered by the U. S. Fish and Wildlife Service (Ref. 7).15 Food availability was determined by estimating ground cover;the amount and taxa of food eaten was determined by estimating and recording evidence of feeding on individual plants.2.2-24 GG ER 16 Field collections and observations indicated that the following) 19 reptilian and 8 amphibian species commonly occurred in the Grand Gulf area: Reptiles Ground skink Green anole Black racer Diamond-backed water snake Common water snake Garter snake Mud snake Hognose snake Gray rat snake Speckled kingsnake Copperhead Cottonmouth Red-eared turtle Three-toed box turtle Stinkpot Mississippi map turtle False map turtle Southern painted turtle Slider (Lygosoma laterale)(Anolis carolinensis)(Coluber constrictor)(Natrixrhombi fera)(Natrix sipedon)(Thamnophis sirtalis)(Farancia abacura)(Heterodon platyrhinos)(Elaphe obsoleta)(Lampropeltis getulus)(Agkistrodon contortrix)(Agkistrodon piscivorus)(Pseudemys scripta)(Terrapene

'iJThna)(Sternothaerus odoratus)(Graptemys kohni )(Graptemys pseudogeographica)(Chrysemys picta)(Pseudemys concinna)Amphibians American toad Fowler's toad Spring peeper Upland chorus frog Gray tree frog Leopard frog Bullfrog Bronze frog (Bufo americanus)(Bufo woodhousei fowleri)(Hyla crucifer)(PTseudacris triseriata)(Hyla versicol0r)(Rana pipiens)(Rana catesbeiana)(Rana clamitans)

Reptiles and amphibians are found in both aquatic and terrestrial habitats.

Since they are poikilotherms 1 7 1 reptiles and amphibians occurring in Mississippi are only active from spring through fall, becoming dormant in the winter.2.2.2.5.1 Reptiles Generally, reptiles of the Lower Mississippi Valley breed during the spring and early summer and young are produced from July to October (Ref. 24). The American alligator and all of the lizards and 16 Most specimens were captured alive, taxonomically identified, and released.17 Poikilotherms are animals whose body temperature varies with the temperature of their environment.

2.2-25 GG ER turtles of the region are oviparougi 8 ,while the snakes may be either oviparous or ovoviviparous.

i9 Literature review of the food habits of reptiles observed on the site (Refs. 25, 26, and 27) indicates that the lizards are primarily insectivorous, although all consume a variety of other invertebrates including snails, spiders and millipedes; the turtles are omnivorous, feeding on plants, fish, carrion and invertebrates; the snakes are carnivorous, consuming a variety of reptiles, amphibians, birds, small mammals and fish; and the alligator is carnivorous, feeding on insects and crustaceans as a juvenile, and larger animals, such as fish, snakes and mammals, as an adult.Field collections inditated turtle, three-toed box turtle, and stinkpot were the most abundant turtles on the site.Reference 24 notes that aquatic turtles normally become inactive when the water temperature drops below 50 F (10 C). Aquatic turtles on the Grand Gulf site were generally inactive from mid-November through late February.

During this period, the mean surface water temperature of Hamilton and Gin Lakes and the Mississippi and Big Black Rivers was below 10 C. Mean surface water temperatures rose above 10 C in March, at which time aquatic turtles become active.The terrestrial box turtle was also generally inactive from December to March. During this period, mean weekly air temperature in the Grand Gulf area was generally less than 10 C. The mean weekly air temperature rose about 10 C in March and the activity of box turtles increased noticeably.

Red-eared turtles, snapping turtles, sliders, and stinkpots dug nests and laid eggs in fields adjacent to Hamilton and Gin Lakes beginning in the latter part of May and continuing through June.Egg deposition began shortly after floodwaters started receding from the bottomlands.

20 Twenty-five water snakes. (representing five species:of Natrix2 were collected:

from stockponds, Hamilton and Gin Lakes, and the flooded The majority were collected between: :,May: 16:-.and June 30, 1973 from shallow pools of water: :that were :created by the ,gradual draining qf floodwaters from the bottomlands.

Many small fish (:largely Centrarchidae (sunfishes) and Cyprinidae (minnows))

were trapped in the pools-and:

apparentlya::tatracted the piscivorous wa:ter snakes. Of the 25 water snakes-collected, 10 were common (broad-banded) water snakes, and 91::::Were diamond-backed water snakes.18 Oviparous animals are those which produce offspring from eggs hatched outside the female's body.19 Ovoviviparous animals are those which produce offspring from eggs hatched within the female's body.20 Species of water snakes collected were the green water snake (Natrix cyclopion), diamond-backed water snake (Natrix rhombifera), yellow-bellied water snake (Natrix crythroguster), common water snake (Natrix sipedon), and Graham's water snake (Natrix grahami).2.2-26 GG ER Collection of terrestrial snakes and field observations indicated that the gray rat snake, speckled kingsnake, black racer, and eastern hognose snake were the most common terrestrial snakes on the site. Field observations indicated that terrestrial snakes..were generally inactive from December 1972 until early March 1973.During this period, the mean weekly air temperature was normally less than 10 C.The American alligator, an endangered species, has been observed on or near the Grand Gulf site since May 1973. Prior to May 1973,.no alligators had been observed on the site; one alligator had been sighted, however, on the bank of the Big Black River in September 1972.. The occurrence of alligators on the site beginning in May 1973 may have resulted from a displacement of alligators from the Big Black River and/or nearby oxbow lakes by the 1973 spring flood.Four alligators were observed during a September 1975 survey of Hamilton and Gin Lakes. One was seen in Hamilton Lake in September 1976, and two were seen in Gin Lake in July 1977. In November 1974 one alligator was found dead (shot) in Hamilton Lake.2.2.2.5.2 Amphibians Amphibians of the Lower Mississippi Valley normally breed during the later winter-spring period, although occasional breeding by toads may occur during any part of the year (Ref. 24). Breeding activity2l of frogs and toads was observed on the site from January to May 1973, with a peak occurring in late February and March. No observations of salamander breeding were made.Literature review of amphibian food habits (Ref. 27) indicates that the adult forms of all amphibian species occurring at Grand Gulf are carnivorous and primarily insectivorous.

However, the larval form of frogs and toads (tadpoles) subsist largely on microscopic plants.The American toad and Fowler's toad were abundant in all terres-trial habitats.

The spade foot toad was only collected in the loessial bluff forest. Frogs inhabited the lakes, streams and stockponds, with the bronze frog being the most abundant.

Of the salamanders, the amphiuma and the lesser siren were collected only in the flooded bottomlands near Hamilton and Gin Lakes., The mole salamander and slimy salamander were collected only in the loessial bluff forest.2.2.2.6 Disease and Pest Infestations in Flora and Wildlife 2.2.2.6.1 Flora Plants and trees are afflicted by a variety of diseases which may cause severe injury and occasionally death to affected vegetation.

21 Observations of breeding activity were based on the vociferous calling of males.2.2-27 GG ER Additionally, plants and trees support thousands of insect species which occasionally become so abundant that severe injury or death is inflicted on host plants in a large geographic area.Review of literature and contacts with Mr. Robert Morris (Ref. 28), Dr. Richard Collins, (Ref. 29), and Mr. Jack Coley, (Ref. 30)., indicated that there are no serious disease or pest infestations currently (1976) occurrina in epidemic proportions in the Grand Gulf region.Mr. Morris and Dr. Collins (Ref. 28 and 29) noted the following:

a. During 1974, plantations of young sycamore trees in the Grand Gulf and New Roads, Louisiana vicinity developed lethal cankers caused by a complex of fungii.b. During the summer and fall of 1974, oak trees in Mis-sissippi, Louisiana, and Arkansas were defoliated by the yellow-necked caterpillar and the orange-striped oakworm.c. During 1975 in Mississippi, Louisiana, and Arkansas oak declines occurred as a result of a complex of diseases with insect involvement which caused the death of oak trees.d. During the 1972 growing season, southern red oaks in southwest Mississippi exhibited an uncharacteristic upward cupping or curling of their leaves. This leaf curling malady has not recurred since 1972. The cause of this leaf curling has not been determined; preliminary results of a study of the affliction by the Mississippi Forestry Commission, however, indicated growth of the afflicted trees was not affected.e. Currently, the Homochitto National Forest is afflicted with a southern pine beetle (Dendroctonus frontalis).

Some disease or pest infestations that were observed on the Grand (Gulf site during the preconstruction studies were: Disease or Pest Infestation Host Vegetation Southern pine beetle Loblolly pine Ips engraver beetle Loblolly pine (Ips spp.)Tent caterpillar Pecans (Malacosms

'disstri)2.2-28 GG ER Rust-type fungi Loblolly pine, dewberry and wood sorrel Gall-producing insects of Southern red oak the order Hymenoptera and the family Chalididae An airborne remote-sensing survey utilizing infrared photography was conducted on October 2, 1972 to document baseline, precon-struction information concerning vegetation assemblages on and adjacent to the Grand Gulf site, and to delineate areas of suspected existing stress or disease within these vegetation assemblages.

Areas of suspected vegetation stress are shown in Figure 2.2-8;the larger areas of suspected stressed foliage occurred in swampy, high-moisture areas. Areas of suspected vegetational stress located on or near the site were at the northern end of Grand Gulf Island and in the Alligator Bayou area adjacent to the southwest boundary of the site.Subseauent inspection of these two areas by an entomologist and a plant pathologist did not reveal any heavy insect pest or plant disease infestations.

In the Alligator Bayou area, some nuttall oak (Quercus nuttallii) trees were dead or dying as a result of increased water levels in the area caused by the impoundment of a small stream by beaver dams.2.2.2.6.2 Wildlife Wild animals are normally subject to various kinds of diseases and serve as hosts for numerous parasites.

In natural communities there will normally exist a variety of viruses, bacteria, proto-zoans, and parasites of higher animal orders to which affected wildlife species have achieved mutual adaptation.

Disease and pest infestations in wildlife populations are usually density dependent (i.e., the greater the population density, the higher the level of parasitism and disease).Review of literature and contacts with Mr. William H. Turcotte, (Ref. 11), Mr. Peter Fusselle, (Ref. 31), and Dr. Annie K.Prestwood, (Ref. 32), indicated that there are no known wildlife diseases or Pest infestations currently occurring in epidemic proportions in the Grand Gulf region.However, Dr. Prestwood (Ref. 32) noted the following:

a. In 1973, high water and food shortages caused severe parasitic infestations (mainly stomach and lung worms)in wildlife.

These infestations occurred in Issaquena and Warren Counties in Mississippi and East Carroll, Madison, Tensas, East Baton Rouge, and Iberville parishes in Louisiana.

b. In 1975 there was an epidemic of Hermorrhagic disease in deer of southeast Arkansas.2.2-29 GG ER 2.2.2.7 Endangered or Threatened Terrestrial Species There are no plants, mammals, birds or amphibians which have been designated as endangered or threatened by the U. S. Fish & Wild-life Service (Ref. 7). One endanqered reptilian species, the American alligator, occurs in Hamilton and Gin Lakes.The Mississippi Game and Fish Commission (Ref. 12) and Mississippi Natural Heritage Program (Ref. 13) have listed endangered and threatened species for the state. With the exception of the American alligator (endangered) and black bear (threatened), none of the species on these lists are known to be present on the Grand Gulf site. Species on the lists which could occur in the vicinity of the site (Ref. 6 and 14) are listed below: Red wolf (Canis niger)Cougar (Felis concolor)Southern bald eagle (Haliaeetus

.. leucocephalus)

Peregrine falcon (Falco peregrinus)

Osprey (Pandion haliaetus)

Eskimo curlew (Numenius borealis)Bachman's warbler (Vermivora bachmanii)

The southern bald eagle, peregrine falcon, eskimo curlew, Bachman's warbler, red wolf, eastern cougar, and American alligator have been designated as endangered by the U. S. Fish and Wildlife Service.The red wolf and puma, are wilderness species which were extirpated from the region as the result:of hunting and destruction of habitat. Suitable habitat for these species is present in much of southwest Mississippi including the Grand Gulf area. A summary of the records of Mississippi land mammals (Ref. 14), however, indicated that the last authenticated 2 2 record of any of these species occurring in this region was in 1946 when a red wolf was collected in Claiborne County.On June 17, 1973, a cougar was sighted near the northeast corner of the Grand Gulf site. Reference 14 notes that cougar sightings are periodically reported in Mississippi, particularly from the Pascagoula Swamp region of George and Jackson Counties in south-eastern Mississippi.

No other cougar sightings were made in the Grand Gulf area, nor was any cougar sign such as tracks or scats encountered during field studies. The cougar may have been tem-porarily displaced from a remote section of the Mississippi River bottomlands by the 1973 spring flood.Black bear, which had not previously been seen on the Grand Gulf site, were first observed on February 2, 1977, when one was seen near basin A. On February 25, another bear was seen in the same 22 An authenticated record normally reauires the collection of the animal for verification of identification by a mammalian taxonomist.

2.2-30 G G ER locality.

Two additional sitings were made in the field in which the meteorological tower is located on March 30, and April 28.vhile no bears have been seen since April, tracks and other sign were observed in the bottomlands just south of the property line.The southern bald eagle, osprey, peregrine falcon, and eskimo curlew may occur in this region, particularly along the Mississippi River during migration.

The Grand Gulf Nuclear Station Project has consulted with the Mississippi Game and Fish Commission (Ref. 11)and has found that the southern bald eagle was known to nest in the Mississippi River bottomland region north of the Big Black River prior to 1960. In recent years, southern bald eagles have oc-casionally been sighted around Yucatan Lake, located across the Mississippi River northwest of the site. An osprey was observed on May 11, 1973 on the western (Louisiana) bank of the Mississippi River about 2 miles southwest of the Grand Gulf site. This was the only osprey observed in the area-during the entire period of preconstruction field studies (June 1973 through August 1973) and this individual was probably migrating north.Rachman's warbler is a very rare species that inhabits moist deciduous woodlands, particularly swamp forests. The most recently recorded observations of this species have been in Virginia and South Carolina.

Records in the Mississippi Museum of Natural Science, consulted by the Grand Gulf Nuclear Station Project, indicated that the species does not occur in the Grand Gulf area.According to the Bureau of Sport Fisheries and Wildlife, the present distribution of the American alligator is from Tyrell County, North Carolina to Corpus Christi, Texas, and north in the Mississippi River drainage to Arkansas and southeastern Okla-homa. Prior to the 1973 spring flood, no alligators had been observed on the site, although one had been sighted on the bank of the Big Black River.Four alligators were counted during a September 1975 survey of the lakes. One was seen in Hamilton Lake in September 1976, and two were seen in Gin Lake in July 1977. One alligator which had been shot and killed was encountered on Hamilton Lake in Novem-ber 1974.2.2.3 Aquatic Ecology 2.2.3.1 Summary The Mississippi River, the Big Black River (a tributary to the Mississippi), and two oxbow lakes, Hamilton and Gin, are the major features of the aquatic environment on and near the Grand Gulf site (see Fiqure 2.2-9). In addition, five small stock ponds (under 2 acres) and two perennial streams with normally negligible 2.2-31 GG ER flow were located on the site. During preconstruction studies in 1972-73, fishes, benthic macroinvertebrates, and plankton were systematically sampled in the two rivers and oxbow lakes and fish sampling was conducted in two stockponds and one of the streams.in addition, periphyton and macrophyton assemblages of the lakes were characterized and sport fishing activities documented.

For purposes of sampling and description, each of the oxbow lakes was treated as a single macrohabitat; the Mississippi River system, however, was divided into backwater, river bank, main channel, and tributary macrohabitats.

Sampling was conducted in the reach of the river extending from mile 400 to mile 410 of the Lower Mis-sissippi River.Backwater habitats in the Mississippi River are located in the slow moving, quiet waters on the inside of large bends, in coves on the leeside of sandbars and islands, in the lower reaches of slug-gish tributaries, and in other similar areas. These backwaters are characterized by zero to low velocity current, relatively shallow waters, and loosely consolidated silty clay sediments of low plasticity.

They typically support an abundant and productive biologic community of fishes, benthos, and plankton.In areas of moderate to swift current, banks of the Mississippi River are usually steep and generally composed of consolidated, highly plastic clay. Clay bank'stability varies greatly, depending on local soil geology, the amount and type of terrestrial vegeta-tion, and the degree of scouring currents.

In areas of stable clay outcroppings, large populations of burrowing mayflies and other invertebrate taxa become established.

Where the bank is constantly eroding, however, benthic organisms are unable to estab-lish a stable population.

The tributary macrohabitat as used in this report is the mouth of the Big Black River which alternates between periods of little or no discharge (backwater) and periods of relatively high dis-charge (tributary).

The substrate typically consists of loosely consolidated silty clays of low plasticity.

The composition and abundance of the fish, benthic, and plankton populations can fluctuate markedly in this type of macrohabitat.

Because of the large area it encompasses, the river channel is the dominant macrohabitat in the site vicinity.

This habitat is characterized by deep water, strong (and turbulent) currents, and coarse-grained substrate, typically consisting of gravelly sand sediments.

The severity of this habitat imposes restrictions on living organisms.

The bottom was found to be virtually non-pro-ductive of benthic organisms, and the water column to contain fewer fish than in other macrohabitats.

2.2-32 GG ER The oxbow lakes, Hamilton and Gin, are relatively small and shallow.At normal water levels, the surface area of- Hamilton Lake covers approximately 70 acres; that of Gin covers approximately 45 acres.In 1973 the mean depth of both lakes was about 5 feet. River-transported sediments, primarily silts and clays, are deposited on the lake bottoms during periodic inundation by Mississippi River floodwaters.

These lakes are similar to river backwater in physical characters, with shallow depth, no current, and loosely consolidated, highly plastic clay sediments.

They generally support productive biotic assemblages.

The bluff stock ponds, constructed to water cattle stock, are small (0.25 to 0.50 acre-each) and unproductive.

These ponds were apparently stocked with fish by previous owners and do not appear to have been managed recently.

The two streams draining the site bluffs are perennial.

Because of their negligible flow, they are not productive fish habitats.Field studies have resulted in the documentation of occurrence on or near the Grand Gulf site of 86 species of fish, more than 100 plankton taxa, and over 50 benthic macroinvertebrate taxa.No endangered fish species are known to be present on or near the Grand Gulf site.2.2.3.2 Fishes Fish sampling was conducted with various frequencies and intensi-ties in the aquatic systems on and adjacent to the Grand Gulf site from June 1972 through August 1973. The aquatic systems sampled included the Mississippi River (mile 400-410), the mouth of the Big Black River, Hamilton and Gin Lakes, site stream A, and two bluff stock ponds.Sampling was conducted monthly from September 1972 through August 1973 for 3 to 15 consecutive days at backwater macrohabitat station 1, river bank macrohabitat stations 3, 5, 6, and 8, and tributary macrohabitat station 10 (see Figure 2.2-9) with various mesh sizes of gill, trammel and hoop nets. Sampling of the river channel macrohabitat (between stations 3 and 6) was conducted once in September 1972 and monthly from June through September 1973 with an otter trawl and fish-locating echo sounder. Periodic sampling of the near-shore macrohabitats at stations 1, 3, 6 and 8 was performed with a beach seine. Nektonic larval fish were systematically sampled monthly or semimonthly at river stations 3 and 6 from January through July 1973. Hamilton and Gin Lakes were generally sampled bimonthly with electrofishing gear or gill and trammel nets from June 1972 through August 1973 (see Figures 2.2-10 and 2.2-11). Site stream A was sampled twice and two bluff stock ponds were each sampled once with electrofishing gear during the study period (see Figure 2.2-12). Sport fishing creel and 2.2-33 GG ER recreation activities were recorded frequently for the Mississippi and Big Black Rivers, Hamilton Lake, and Gin Lake from April through August 1973. Mississippi River commercial fishing creel census was conducted during January and February 1973.Sampling with fish nets and electrofishing gear was standardized so that valid comparisons of temporal changes in fish catches among macrohabitats could be made. Each net was set and fished for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (a net-day) if conditions permitted.

River condition, river stage, weather conditions, and equipment problems (e.g., lost, torn or clogged nets) occasionally required modifications of the planned schedule and procedures.

Data on fish catches with nets and electrofishing gear were transformed to catch-per-unit-effort bases for comparisons among water bodies and macrohabitats.

Fish diet was characterized in a preliminary study for 13 fish species collected from the river and Hamilton Lake. Reproductive periodicity of river fishes was inferred from spawning condition of adults and from detailed densities of larval fishes. Popula-lation density and standing stock estimates of near-shore fishes in the Mississippi River and in site stream A were made using the population removal method of Zippin (Ref. 33). Population density and standing stock estimates in the two bluff stock ponds were made using the Peterson mark-recapture method (Ref. 34); confidence intervals were placed around these estimates using the method suggested by Adams (Ref. 35). Occurrence of fish disease and parasites was recorded during regularly scheduled field collecting activities; data on these occurrences are presented in subsection 2.2.3.6.2.2.3.2.1 Species Collected The Lower Mississippi River suffered a catastrophic fish kill from Memphis to the river mouth in 1963-1964.

Endrin, a chlorinated hydrocarbon, was demonstrated to be the cause of the heavy mor-talities (Ref. 36). The fish population appeared to recover rapidly when the industrial releases of endrin in Memphis were discontinued after 1964. A notable exception to this recovery was the absence of large specimens of long-lived fish (e.g., cat-fish, buffalo and drum) when the population was surveyed in 1966-1968 by the Lower Mississippi River Technical Assistance Project (Ref. 36).A total of 86 species (20 families and 42 genera) were collected from the waters on or adjacent to the Grand Gulf site from June 1972 through August 1973. Sixty-nine species were collected from the Mississippi River, which compares favorably with the 69 species collected in a similar study conducted for a proposed nuclear station at St. Francisville, Louisiana, approximately 136 miles downstream in 1972-1973 (Ref. 37).2.2-314 GG ER The results from both of these studies indicate a lower species diversity than was expected prior to commencement of field studies at Grand Gulf, when as many as 110 species had been expected.

A survey of the Upper Mississippi River listed 134 species, of which 30 were considered stragglers and not normal inhabitants of the river (Ref. 38). Since fish species diversity generally increases from headwater to river mouth, the original list of 110 species should be a realistic estimate.

If so, the endrin kill in the early 1960s may have reduced species diversity by extirpating some species which were highly sensitive to the chlorinated hydro-carbon pesticide.

Although extended flooding tends to disrupt normal habitat distri-butions of fishes, some distinct patterns in both species diversity and habitat distribution were noted among the water bodies on or adjacent to the Grand Gulf site. The Mississippi River was the most diverse environment, containing several major macrohabitats in the site vicinity (i.e., backwater, river bank, channel, sandbars).

This diversity is reflected by fish species distribution:-

69 species were collected from the Mississippi River compared to 49 species in the Big Black River.The following species were collected only in the Mississippi River:)Chestnut lamprey Pallid sturgeon Shovelnose sturgeon Goldeye Mooneye Speckled chub Sicklefin chub Sauger Walleye Quillback Highfin carpsucker Lake chubsucker Blacktail redhorse Yellow bullhead Brown bullhead Stonecat Tadpole madtom Freckled madtom Striped mullet (Ichthyomyzon castaneus)(Scaphirhynchus albus)(S caphirhynchus platorynchus)(Hiodon alosoiaes)(fiodon terqisus)(Hybopsis aestivalis)(Hybopsis meeki)(Sti zosted-on canadense)(Stizostedion vitreum)(Carpiodes cyprinus )(Carpiodes velifer)(Erimyzon sucetta)(Moxostoma poec lurum)(Ictalurus natalis).(Ictalurus nebulosus)(Noturus flavus)(Noturus qyrinus)(Noturus nocturnus)(MuTicephalus)

Several of the species collected were distributional records.Identification of a pallid sturgeon specimen (Scaphirhynchus albus, Forbes and Richardson) was confirmed by Bailey (Ref. .39); the specimen has been reposited in the Museum of Zoology, University of Michigan.

Prior to this recorded collection, this species was known only from two locations in the entire Mississippi, the mouth of the Missouri River and the Mississippi River at New Orleans.)2.2-35 GG ER Two specimens of the sicklefin chub (Hybopsis meeki, Jordan and Evermann) were collected from the intake screens of MP&L's Baxter Wilson Steam Electric Station at Vicksburg.

Prior to these collections, this species had never been recorded in the Mississippi River south of the mouth of the Ohio River (Ref. 40). One speci-men of a newly described species, Hybopsis winchelli, Clemmer, was also collected from the Mississippi River (Ref. 40).A number of fish species occurred in both oxbow lakes and in the Mississippi River. Although the lakes are similar morphometrically, Hamilton Lake appears to have a more diverse species composition:

46 species were collected in Hamilton versus 36 in Gin. One possible reason for this difference is the relationship of the lakes to the river. Hamilton Lake has a direct connection through which fish can pass between the river and the lake when the river elevation is above 56 feet msl. However, Gin has no direct connection with the river except during very high river stages (greater than 63 feet msl). Evidence of this interaction was recorded in both the fall of 1972 and the succeeding summer of 1973.When the river first began flowing into Hamilton Lake (November 7, 1972) at the beginning of the flood, fish were caught on the river side of a trammel net placed in the outfall, indicating movement into the lake from the river. At that time, the stomach of a blue catfish (Ictalurus furcatus) captured in the net was examined.

The fish had consumed the mayfly nymphs Hexagenia and Pentagenia.

Neither of these mayflies had been previously collected in the lakes, although they had been recorded at river stations.

It was inferred that the catfish had been feeding in the river and had subsequently tried to enter the lake.Large numbers of young-of-the-year paddlefish (Polyodon spathula)were observed 2 3 in both lakes in July 1973, after the river and lakes were separated.

A rise in river stage in early August 1973 again made the river and Hamilton Lake confluent.

When these water bodies were subsequently separated, the number of paddlefish had decreased, indicating they were probably recruited to the river population.

Site stream A contained 21 fish species, some of these were indi-genous: the striped shiner 2 4 (Notropis chrysocephalus), blunt-nose minnow (Pimephales notatus), creek chub (Semotilus atromacu-latus), and redf in darter (Etheostoma whipplei).

These four species generally occur in stream environments and have been noted in streams draining the Vicksburg bluffs (Ref.41).

The two bluff ponds were low in species diversity:

Pond 1 contained bluegill (Lepomis 23 Visual observation only; attempts to collect these fish were unsuccessful.

24 A subspecies of the common shiner (N. cornutus).

2.2-36 GG ER macrochirus) and mosquitofish (Gambusia affinis);

and Pond 2 had a large population of bluegill and mosquitofish and a few channel catfish (Ictalurus punctatus).

During extensive flooding, such as recorded in the spring of 1973, fish are often displaced from their normal habitat. When the near-shore environment of the Mississippi River was displaced by flooding, in some cases a considerable distance from the river bank, fishes of this habitat apparently moved inland abandoning what had been beaches and sandbars.

This movement was indicated by a sharp decrease in the abundance of minnows from before the flood (Septem-ber 1972) and later during the flood (January, 1973) at two river stations.

Fishes of this near-shore environment (e.g., silvery minnow (Hyboqnathus nuchalis) and emerald shiner (Notropis atheri-noides)) were subsequently collected in shallow floodwaters at the base of the bluffs, east of the oxbow lakes. It is possible that normal species-habitat distribution in the Grand Gulf vicinity may be more restricted than that observed during the preconstruc-tion study.2.2.3.2.2 Adult Fish Assemblage

-Mississippi and Big Black Rivers a. Backwater, River Bank and Channel Habitats 1. Numbers and Weights Net sampling from September 1972 through August 1973 produced 3710 fish which weighed 2 5 5430 pounds. Forty-seven species were collected.

Gizzard shad (Dorosoma petenense) were markedly dominant in numbers (37 percent of the total).This species showed marked temporal fluctuations in abundance during the year, varying from 3 to-76 percent in relative numerical abundance.

Gizzard shad abundance also varied spatially.

From September 1972 through January 1973 and from April through August 1973, they were most abundant in backwater habitat. However, in February very high numbers occurred in the river bank habitat. The appearance of nektonic larval shad in March indicated a possible seasonal spawning movement had occurred in February.Four other species comprised at least 5 percent (numerically) of the river population:

fresh-water drum (Aplodinotus grunniens)

(10 percent), blue catfish (Ictalarus furcatus)

(8 percent), flathead catfish (Pylodictis olivaris)

(5 percent), 25 All weights were taken on live specimens except in September and October 1972. Weights of most specimens collected in August 1973 were estimated from lengths using least square regressions.

2.2-37 GG ER and river carpsucker (Carpiodes carpio) (5 percent).The numerical abundance of shovelnose sturgeon (Scaphirhynchus platorhynchus)

(3 percent) is note-worthy because numbers of this species have ap-parently declined significantly in recent years (Ref. 42) and concern has been expressed for sur-vival of the species (Ref. 43). It appears how-ever, that an abundant population may exist in the Grand Gulf vicinity.Carp (Cyprinus carpio) ranked eleventh in numerical abundance (2 percent of the total). This contrasts to their high abundance in the Upper Mississippi River where they are a dominant commerical fish, exceeded in catch only by buffalo fishes and-drum (Ref. 44 and 45). They were also one of the most abundant fish reported from the study conducted in the Mississippi River at Vicksburg during 1966-1968 (Ref. 36).Fish biomass in the river was more evenly distrib-uted and no one species dominated to the extent seen in numerical abundance.

The dominant fish smallmouth buffalo (Ictiobus bubalus) comprised 14 percent of the total biomass. Biomass domi-nance by this species was largely due to species configuraton; specimens up to 25 pounds were recorded in field collections, and up to 35 pounds were recorded in the commercial fisherman creel census. Flathead catfish (14 percent), gizzard shad (10 percent), freshwater drum (9 percent), and blue catfish (9 percent) ranked next in biomass abundance.

Carp (7 percent) were sixth in biomass abundance.

It is probably significant that, with the exception of the gizzard shad, fish of commercial value con-stituted the first 10 most numerically abundant species in the total catch. This is particularly noteworthy since no attempt was made during field sampling to'collect only these species.2. Habitat Distribution

-Spatial Differences in the five numerically abundant species occurred among backwater (station 1), river bank (stations 3, 5,6, 8), and tributary (station 10)macrohabitats.

Gizzard shad were numerically dominant in all three habitats, ranging from 18 percent in the tributary habitat to a marked dominance of 52 percent in the river bank habitat.2.2-38 GG ER The five most abundant species in the backwater at station 1 were gizzard shad, blue catfish, river carpsucker, freshwater drum, and shovelnose sturgeon.A total of 35 species were collected with nets in this backwater.

Eighty-five percent of the backwater fish assemblage was comprised of 10 species, of which two sport species, white crappie (Pomoxis annularis) and black crappie (Pomoxis nigromaculatus) made up 11 percent.In contrast, of the 34 species collected at river bank habitat stations, the following were most abundant:

gizzard shad, freshwater drum, silver chub (Hybopsis storeriana), flathead catfish, and blue catfish. The abuidance of silver chub indicates a preference by this minnow for moving water. How-ever, they were more abundant in moderate current than in swift current: 80 percent of the silver chub were collected at stations 5 and 8, while the remaining 20 percent came from stations 3 and 6. Surface current velocities at stations 5 and 8 were lower than those at 3 and 6. In contrast, drum were more abundant on the east side of the river in swifter current; 61 percent of those collected at river bank stations came from stations 3 and 6. Flathead catfish and shortnose gar (Lepisosteus platostomus) (fourth and seventh, respectively) were seasonally abundant at river banks. Flathead catfish were about equally dis-tributed between the east and west banks; 26 of the 29 shortnose gar collected, however, were captured at station 3. Most of these gar were collected in February in hoop nets which also contained large numbers of gizzard shad, indicating the gar may have been preying on the shad. Bigmouth buffalo (Ictiobus cyprinellus), eighth in numerical abundance, were caught primarily in river bank habitat. These catches, considered with catches recorded in commercial fishing creel censuses, indicated a preference by this species for moderate to swift current habitats, unlike the smallmouth buffalo which appeared to frequent backwater.

The fish assemblage of the Big Black River was not easily characterized because of the physical varia-tion which occurred during the study period. The river varied from backwater, to a moderate current stream, to a flooded stream with high current velocity.

Based on catches from September 1972 through August 1973, the following species were 2.2-39 GG ER most abundant in the Big Black: gizzard shad, shortnose gar, blue catfish, freshwater drum, and smallmouth buffalo. Twenty-eight species were collected.

Channel catfish were more abundant in this tributary habitat (4 percent) than in back-water (<0.1 percent).

There abundance fluctuated widely throughout the year and was highest in June 1973 during the period that floodwaters were rapidly receding.

At this same time, sport fishermen reported high trotline catches of catfish in the floodwaters adjacent to the Big Black River and the two lakes. Fifteen blue suckers (Cycleptus elongatus) were collected in October and November in the Big Black; none were encountered subsequently.

Local fishermen report that the Big Black River is the only water body this species inhabits in the Grand Gulf vicinity (Ref. 46). Their distribution appears to be restricted to the Missouri River in the Upper Mississippi River Basin (Ref. 44), and they apparently are not common in the Missis-sippi River proper.The fish assemblage of the river channel habitat was the most difficult to characterize because of sampling limitations imposed by physical conditions (e.g., turbulent, swift current; irregular bed con-figuration; bottom-associated debris). Two trawl efforts on September 13, 1972, in the vicinity of station 6, yielded no fish. Trawling was then dis-continued until June 1973 because of flood condi-tions. Nineteen trawl efforts between June 7 and July 18 yielded a total of 92 fish and 5 river shrimp for a mean catch per effort (+ standard deviation) of 5.2 +8.7 organisms.

All the fish collected in June and July were young-of-the-year; the river shrimp were large adults.Gizzard shad'and drum were the most common species encountered.

These fish were probably being carried downriver by the current and were probably not a resident population of fish. July surface meternet samples indicated an increased density of young-of-the-year shad and drum in larval fish samples. This occurred concurrently with a large increase in rate of impingement of organisms at the Baxter Wilson Steam Electric Station approximately 30 miles up river from Grand Gulf, particularly young-of-the-year shad and drum. Echo sounder traces taken con-currently with the July 18 trawls indicated a con-centration of small fish in the upper 10 feet of water. This information suggested that the fish 2.2-40 GG ER collected in the trawls may have been near the water surface and captured while the trawl was being played out or retrieved.

A series of echo sounder traces was taken parallel and perpendicular to the current on July 19 in an attempt to determine vertical and horizontal fish distribution.

These traces were taken on ranges located between stations 3 and 6. A representative pair of traces were selected for analysis.Horizontal distribution appeared to be fairly homo-genous and approximated an even distribution.

Verti-cal distribution, however, was clumped; highest numbers occurred at the river surface (4 to 10 foot depth) and at the bottom (40 to 50 foot depth), while the 10 to 30 foot depth was virtually devoid of fish traces. One parameter possibly affecting this distribution is water velocity.

A line con-necting the mean number of traces at each depth interval appeared to approximate a vertical velocity profile. Assuming this is a good approximation, fish distribution could be related to velocity.

At highest velocity (20 to 30 foot depth), few fish occur, probably because of their inability to withstand the current. At the surface (4 to 10 foot depth) and bottom (40 to 50 foot depth), current was probably reduced enough so fish could partially maintain a position in the water column.However, trawl sampling in August 1973 indicated a possible resident population of fish in the channel.Young blue and channel catfish, shovelnose sturgeon, and specimens of four chub species were collected.

A similar collection in September 1973 (although with reduced species diversity) strongly indicates these fish were resident in the channel during these 2 months. Current velocities near the bottom of about 1 foot per second, measured on September 25, lend support to this possibility.

The sizes of the fish collected in August and Septem-ber 1973 suggest a population composed primarily of juvenile fish. However, since larger fish probably easily escaped the trawl and avoided capture, the collections are probably biased toward smaller fish.Because of the presence of these juveniles in the main river channel, it is reasonable to assume that larger and older fish are also present. Also, echo sounder traces indicated the surface population present on July 19, 1973 was considerably reduced in number.2.2-41 GG ER 3. Habitat Distribution -Temporal Temporal fluctuations in fish abundance in various river habitats result from such factors as season (reproductive periodicity), water temperature, photoperiod, behavioral patterns, river stage, and current velocities.

Additional variation in sampling results comes from the influence of physical factors (e.g., river stage, current velocities, and debris)on gear efficiency.

Variations in gear efficiencies and in fishing efforts with gill, trammel, and hoop nets result in catches which are not directly com-parable. Catch-per-unit-effort calculations correct for these variations and express catches on a unit basis (i.e., per net day or 24-hour fishing period).These units can then be compared between time periods and habitats.Backwater numerical catch per effort was high in the fall of 1972 (station 1 in October, station 10 in November) but decreased to fairly constant levels from November 1972 through June 1973. Catch success at station 1 in August 1973 returned to the level observed in the previous fall. In contrast, river bank catches per effort at stations 3, 6 and 8 were low through January, increased significantly in February, then decreased to former levels in April and June; a small increase occurred in August.The rather large numerical catches per effort in October and November 1972 at stations 1 and 10 and again in August 1973 at station 1 may be indicative of seasonal increases in fish abundance in backwaters.

Concomitantly, fish abundance in river bank habitats also appeared to fluctuate seasonally.

The increased abundance in February in the river bank habitat occurred at the same time ripe fish were observed and occurred just prior to the appearance of larval fish in March. Apparently, these fish were parti-cipating in movements preparatory to spawning.Weight catches per effort generally showed a pattern similar to numerical catches. The only exception was the high weight catch and low number catch at station 1 in September 1972. This was due to the collection of several rather large catfish which contributed significantly to the total weight catch.Weight catch per effort in February at river bank stations did not show as large an increase as did numbers because gizzard shad made up most of the 2.2-42 GG ER numerical increase.

Since the average weight of these shad was only 0.3 pound, their relative con-tribution to the average weight catch was less than that of several large catfish caught at station 1 in September 1972.The number of fish species caught per effort was low in all periods at all stations.

Lowest (0.04) and highest (2.62) values were recorded in the Big Black River (station 10). The number of species caught per effort does not appear related to either number or weight catch per effort. This was evident both at individual stations and in mean catches for all stations.

Although significant fluctuations in both mean number (0.83 to 5.17) and mean weight (1.3 to 9.1 pounds) catches per effort occurred, mean species catch per effort showed little fluc-tuation (0.53 to 1.53).4. Diet Food items consumed by adults of 13 fish species collected from Mississippi River stations 1, 10 and 1326 and Hamilton Lake, were identified and enumerated.

Data from this preliminary study indicated that thread-fin and gizzard shad were an important food source for some fish species. Catfish, crappie, skipjack herring (Alosa chrysochloris), white bass (Morone chrysops), and largemouth bass (Micropterus salmoides) had fed mainly on fish, principally shad. When benthic macroinvertebrates were eaten, some fish species appeared to feed selectively.

Flathead and blue catfish at station 1 preyed primarily on mayfly numphs (Hexagenia and Pentagenia) which, although low in relative numerical abundance (ca. 4 percent), comprised approximately one-third of the benthic standing stock at station 1. Crappie and drum, however, cropped primarily dipteran larvae in this backwater.

Carp fed on benthic macroinvertebrates (dipteran larvae and bivalves);

river carpsuckers fed on cladocerans and diatoms.Shovelnose sturgeon appeared to feed selectively on benthic organisms in the backwater at station 1.A single specimen collected in November 1972 had consumed primarily tubificid worms, the numerically 26 Reconnaissance sampling was conducted at-station 13 in October 1972;this station was not sampled subsequently.

The station was located in a backwater cover on the east bank of the river at about river mile 413.2.2-43 GG ER dominant organism in the benthic assemblage.

However, 10 specimens collected in April 1973 had consumed mainly Cryptochironomus (62 percent) of all organisms consumed and dipteran pupae (31 percent).

These two taxa comprised less than 1 percent of the benthic organism density in April at station 1.Results of fish diet analyses generally agreed with those of other published reports, except in the case of the white bass. Chadwich (Ref. 47) reported that white bass from Texas, Iowa and Wisconsin had preyed on fish, insects (mayflies), crustaceans (crayfish), and cladocerans (Daphnia).

The white bass examined at Grand Gulf were entirely piscivorous.

Field observations made during net sampling indicated gar are piscivorous, although no stomach content analysis were performed.

Gar captured in trammel and gill nets were almost always ensnared by their teeth.Partially eaten net-trapped fish were generally found with these gar. Apparently, the gar became entangled while feeding on net-caught fish. Also, hoop nets at station 3 in February often held 40 to 60 gizzard shad per net. These shad were generally accompanied by several gar, the only time significant numbers of gar were collected at a river bank station.b. Near-Shore Habitat 1. Species Composition The near-shore habitat of the Mississippi River was characterized by a variety of substrates and a range of current velocities.

At station 1, the dominant near-shore habitat was a large sandbar (towhead)characterized by moderate current velocity and sand substrate on the channel side, and no current and silt-clay substrate on the leeward side from the channel. The depth gradient was gradual. The near-shore habitat at station 8 was also composed on a sandbar with moderate current, coarse, well-graded sand substrate and a shallow depth gradient.

In contrast, both stations 3 and 6 were strongly influenced by swift currents which actively eroded the steep clay banks.The habitat characteristics influenced sampling efficiency, and, consequently, the results obtained.Areas of shallow depth gradient and moderate or no current (stations 1 and 8) were relatively easy to sample. Areas of swift current and steep banks 2.2-44 GG ER (stations 3 and 6) were more difficult to sample, and catches may misrepresent the resident population.

The data reported for station 3 in this case is an exception, however, because the sample was taken during flood stage (January 1973) at which time the water was outside the river bank and flowing slowly over a shallow gradient, gravel-base boat landing.Prior to August 1973, the dominant species in catches from all near-shore areas were threadfin-shad, emerald shiner, river shiner, silvery minnow, mosquitofish, Mississippi silverside (Menidia audens) and juvenile gizzard shad. Between habitats, however, there were distinct differences in dominant species.The area of no current and silt-clay substrate at station 1 (essentially a pothole) was dominated by mosquitofish, Mississippi silverside.

and juvenile gizzard shad. The apparent habitat similarity of the moderate current sandbars at stations 1 and 8 was contradicted by the species composition.

At station 1 in September 1972, the two most abundant species were silvery minnow and river shiner. In the same month, threadfin shad and emerald shiners were numerically dominant at station 8, whereas silvery minnows and river shiners ranked third and fourth in abundance.

At station 3 in January 1973, river and emerald shiners shared dominance and com-prised about 85 percent of the sample.In August 1973, the fish assemblage in the no current habitat at station .1 was dominated by young-of-the-year threadfin and gizzard shad and by silvery minnows.This species composition was significantly different from that observed in September 1972 when mosquito-fish and Mississippi silverside dominated.

No mosquitofish were collected in August and Mississippi silverside ranked eighth in abundance.

Red shiners (Notropis lutrensis), fourth in abundance, were not present in the sample taken in September 1972.The fish assemblage in the moderate current habitat at station 1 also changed significantly between September 1972 and August 1973. Young-of-the-year channel catfish and mooneye, and silver chub dominated the August sample. Neither the silver chub nor the mooneye were collected in the previous September.

Young-of-the-year drum, fourth in abun-dance, were also not present in September samples.River shiner (Notropis blennius) second in abundance in September, were not collected at all in August.2.2-45 GG ER Silvery minnow, dominant in September, ranked only fifth in August in numerical abundance.

Young-of-the-year white crappie comprised 5 percent of the August sample, perhaps indicating high survival success of that year's class.In summary, prior to the 1973 flood, the near-shore fish population of sandbars was dominated by thread-fin shad, emerald shiners, river shiners and silvery minnows; their numerical rank varied among various microhabitats (i.e., individual sandbars).

The single collection from station 6 had too few fish to charaterize the population, except to suggest that total abundance' was probably lower in swift current and steep bank habitats than in other near-shore environments of the river.The near-shore fish assemblage at station 1 changed significantly in dominant species composition between September 1972 and August 19.73. The two habitats (no current and moderate current) supported a distinct and different assemblage at both times. High numbers of young-of-the-year channel catfish, mooneye, drum and white crappie indicated strong 1973 year classes.The cause(s) of changes in species composition is (are) unknown; however, a major influence was probably the extensive flood of 1973. The near-shore habitat at station 1 was essentially vacated by fish during the flood. Repopulation of the void after the flood appeared to result in a different near-shore fish assemblage.

2. Population Estimate The collection from station 3 was not taken in the normal steep bank and swift current habitat. The sample was taken during flood stage at which time the water was outside the river bank and flowing slowly over a shallow-gradient, gravel-base boat landing immediately adjacent to the station. Since it was taken in the immediate vicinity of the near-shore habitat, however, it was considered representa-tive of the local population.

The catch at station 3 was less than at station 1 in terms of number of individuals, number of species and total weight.The numerical population estimate (+ standard devia-tion) (Ref. 33) for station 1 (246 T 3.30 per 0.04 acre) was about twice that for station 3 (140 + 1.19 per 0.04 acre). Expressing these estimates on-the basis of a hectare of water, station 1 contained 13,494 fish (5463 fish per acre) weighing 66.6 pounds 2.2-46 (26.9 pounds per acre). Station 3 contained 7680 fish (3109 fish per acre) weighing 20.1 pounds (8.1 pounds per acre). Difference in river stage and season may have influenced these density varia-tions, but habitat differences were probably the major factor influencing differing fish abundances.

3. Unusual Observations From September 1972 through August 1973, 113 shovel-nose sturgeon were collected from the Mississippi River. The mean standard length of these fish was 25.8 inches and the mean total weight was 0.99 pounds.Thirty-two (29 percent of the total) of these fish showed some damage to their pectoral fins by rubber bands. These rubber bands were stretched tightly over the fish dorsum and against the pectoral fins.The rubber bands had cut into the fins, or had cut one or both fins completely off at the endoskeleton girdle joint (clethrum).

Fins had not regenerated on eight (25 percent) of the damaged specimens, resulting in healed-over stumps on the fish. Regen-erated fins were deformed, typically cupped in appearance rather than flat like a normal fin.The rubber bands were usually 2.4 to 3.9 inches in length (non-stretched) and approximately 0.08 inch in thickness.

The origin of the rubber bands is unknown, although municipal discharges are suspected.

The density of bands in the river is also unknown;a number of them have been observed on the screens of the intake structure of the Baxter Wilson Steam Electric Station.The occurrence of rubber bands on sturgeon probably results from its external anatomy which is comprised of spinous dermal plates. The posterior spine orienta-tion makes it difficult, or perhaps impossible, for the fish to rid itself of a rubber band once it has slipped over its body. It is unfortunate that this species, whose numbers are depleted (Ref. 43) should be anatomically adapted to collect rubber bands.On June 20, 1973, a large number of young-of-the-year bullheads were observed schooling in floodwaters ad-jacent to Bayou Pierre. At least 50 schools were seen, each probably an individual cohort recently emerged from their nest; the total number was estimated at 50,000. Specimens from several schools were identi-fied as yellow bullheads (Ictalurus natalis).

Daily observations indicated that as the floodwater receded, many of these fish were recruited to Bayou Pierre via a small drainage ditch.2.2-47 GG ER 2.2.3.2.3 Larval Fish Assemblage

-Mississippi River Fish reproduction in the Grand Gulf vicinity in 1973 was investigated by systematic collections of nektonic larvae at Mississippi River stations 2 and 6.Low densities of larval fish were first noted in early March.Larvae of seven taxa were collected at that time, indicating some species had commenced spawning.

Shad, Mississippi silverside, stoneroller, and mosquitofish larvae were the most abundant species in this early spawning group.Spawning activity increased significantly by early April. Increased number and taxa of larvae occurred at both stations.

Densities generally increased through April and May to a peak in June. De-creased densities from June through mid-July indicated peak spawn-ing activity occurred in April and May. Although major spawning activity appeared to have occurred before July, significant numbers of larvae were encountered as late as July 17. This indicated spawning by some species probably will occur into the fall, although total densities may continue to decrease at a slow rate.Prior to May 23, nocturnal densities tended to be larger than diurnal densities.

After May 23, however, diurnal densities were consistently larger. Although none of these differences were statistically significant 2 7 , they may indicate a trend of increased larval activity in the daytime. If it is assumed many of these larvae were hatched in backwater habitats and swept into the main river by currents, increased diurnal activity would make them more susceptible to this action in the daytime and account for the higher densities.

This is not an unreasonable assumption since larvae have been demonstrated to follow diel vertical and horizontal migration patterns in Lake Texoma, a large impoundment reservoir on the Red River (Ref. 48). Larvae in the Mississippi River may also follow similar behavioral patterns.Differential densities at the two sampling stations are more diffi-cult to explain. Station 3 densities were always greater than those at station 6, except on March 12 when they were equal, albeit quite small. Higher density at station 3 may have resulted partially from drainage out of the bottomlands and oxbow lakes. Since these bottomlands provide abundant cover and vegetation for species whose eggs are adhesive, they were probably a major spawning area.Floodwaters moving through the area would tend to carry larvae into the river. Conversely, currents at station 6 tended to flow from the river into the bottomlands.

Current patterns in the river proper may also have influenced dif-ferential densities.

Station 6 was located downstream of a clay bank outcropping which deflected much of the current away from the 27 Tested by Student's "t" test for independent means.2.2-48 GG ER station. However, at station 3 there was no outcropping to deflect the current, and surface velocities were generally greater than those at station 6 (see Figure 2.2-13). These two factors, bottomlands and river current patterns, probably were major factors causing higher densities of larval fish at station 3.As noted previously, although densities varied between sampling periods, overall density shows a general pattern of increase from March through June and a subsequent decrease through mid-July.Within this time period, however, densities of various taxa fluctuated greatly. Several taxa showed definite periods of reproduction.

Shad, the most abundant taxa throughout much of the period, ap-parently spawned over an extended period. The major spawning began in early.April, peaked in May and June, and extended through July. Some spawning may also have occurred in August, although it appears from the data that a significant amount of spawning probably did not extend beyond mid-July.

Drum, however, appeared to spawn over a shorter time period and may have had two major spawning periods. Significant numbers of drum larvae appeared in late May, peaked in June, and decreased sharply by early July.Larvae density increased again in mid-July, indicated another spawning population may have reproduced in late summer.Starrett (Ref. 49) reported three distinct groups of spawning populations of minnows in the Des Moines River based on "examination of gonads, appearance28 of young, and literature references".

The three groups, as proposed by Starrett, are: a. Early spawners, i.e. later spring or early summer b. Intermittent spawners, i.e. through warmer months of the year c. Late spawners, i.e. late July through August Starrett also noted that floods and silt appeared to be the major factors reducing reproductive success in the Des Moines River minnow populations.

The abundant minnow species were late spawners which reproduced during periods of low water level and reduced silt loads.The groups proposed by Starrett may apply to the Mississippi River in the Grand Gulf vicinity.

Large numbers of minnow larvae were collected in April, essentially late spring in this area. The stoneroller, one of Starrett's early spawners, were collected only on March 12 and April 4. Large numbers of minnow larvae again occurred in June and July, with highest densities occurring 28 The time young appeared in his samples.2.2-49 GG ER in July. This group may belong to Starrett's late spawner group.Minnow larvae occurred throughout the entire sampling period;some of these could be called intermittent spawners.

Since none of these larvae, except the stoneroller, were identified to genus or species, it is difficult to say whether the minnow population around Grand Gulf follows Starrett's proposal.

The periodicity of larvae densities strongly suggests, however, that there may be similar reproductive patterns.Two taxa which were abundant in the river as adults, catfish and suckers, were conspicuously absent as larvae. This absence of larvae is probably due to their reproductive behavior.

Catfish build shallow depression nests in backwater and the male guards the young until they are strong swimmers (Ref. 50). These young fish are probably able to avoid being swept into the river by currents.

Suckers (e.g., buffalo and carpsuckers) typically move into tributaries, sometimes to the headwaters, to spawn (Ref. 50). Since the Grand Gulf collections were made in the main river, it is unlikely that many catfish and sucker larvae would occur.In summary, major spawning activity of fish started in March and extended at least through July. Peak spawning probably occurred from mid to late May; larval densities were maximum in June. A pattern of diel movements by larvae was inferred from observed differences in diurnal and nocturnal densities.

Although none of the differences were statistically significant, a pattern of higher diurnal densities was observed from late May through July.Conversely, prior to late May, a general pattern of higher noc-turnal densities occurred.

Several taxa-specific reproductive periods were identified.

Shad apparently spawned over a period of 4 to 5 months, with maximum spawning occurring in May and June. Drum appeared to spawn over a shorter period; addi-tionally, there were possibly two periods, early and late summer.Minnows appeared to follow three reproductive patterns, similar to those in the Des Moines River. These patterns, early spawners, intermittent spawners and late summer spawners, were inferred from observed periodicities in minnow larvae densities.

Reproductive periodicity of catfish and suckers probably cannot be inferred by larval collections in the river; because of their reproductive behavior, the larvae develop into juveniles in backwaters and tributaries before they appear in the river.The eggs of most freshwater fishes have at least two characteris-tics: they are demersal (sinking) and adhesive.

Eggs are typi-cally spawned in backwaters where they adhere to substrates like vegetation or logs; or they are spawned over gravelbars and sand-bars, and adhere to the bottom during development (Ref. 50).The freshwater drum produces eggs'which are pelagic in character and develop while floating at or near the water surface (Ref. 45 and 51). The eggs are quite small, ranging from 0.02 to 0.3 2.2-50 GG ER inches in Lake Erie drum (Ref. 51). Larval fish collections with a 0.02 inch-mesh plankton net will infrequently collect fish eggs. During the entire study period, a total of 20 fish eggs were collected; a total of 16,596 larvae were collected.

The density of these eggs was always less than 0.00003 per cubic foot of water.2.2.3.2.4 Adult Fish Assemblage

-Hamilton and Gin Lakes Oxbow lakes periodically inundated by Mississippi River floodwater are potentially dynamic systems in comparison to lakes which are closed systems. Population density stresses caused by high year class survival in one year can be balanced by dispersal during annual flooding.

The potential for fish populations to readjust should lead to balanced populations over a period of years. The studies conducted at Grand Gulf during 1972-1973 suggest the influence of the Mississippi River on the fish populations of Hamilton and Gin Lakes. A 1-year study is insufficient, however, to indicate long-term trends in river-lake interactions.

Although apparently similar habitats, the lakes appear to have discrete fish fauna. Hamilton Lake collections yielded 46 species while Gin Lake yielded 36 species from June 1972 through August 1973. This higher species number in Hamilton was first indicated in collections made in June 1972 when 26 species were collected in Hamilton and 16 species in Gin.The presence of more species in Hamilton Lake may be due, in part, to its more frequent connection with the Mississippi through its drainage outfall (as discussed in subsection 2.2.3.2.1).

Eight of the species collected only in Hamilton Lake were "stragglers", i.e., species which normally inhabit the river. They included the silver chub, emerald shiner, silverband shiner (Notropis shumardi), weed shiner (Notropis texanus), blacktail shiner (Notro is venustus), bullhead minnow (Pimephales vigilax), blue sucker ,and yellow bass (Morone mississippiensis).

Red shiners, collected only in Gin Lake, were probably also river "stragglers".

Although the total species assemblage was more diverse in Hamilton, gizzard shad, bluegill, threadfin shad, and largemouth bass were dominant in both lakes, comprising about 80 percent of the popu-lation. The numerical abundance composition in Gin Lake is based entirely on electrofishing collection; although net sampling was conducted in January and February, the samples were considered too small to be representative.

Net sampling efforts in Gin comparable to those in Hamilton may have resulted in similar abundance of gizzard shad and bluegill.These two species (bluegill and gizzard shad) occupied separate habitats in the lakes. Gizzard shad were the numerically dominant open-water fish in both lakes, comprising about one-quarter of 29 Apparently restricted to Big Black River in local distribution.

2.2-51 GG ER the total population in each lake. Bluegill dominated the shore-line-cover habitat in both Hamilton and Gin and comprised about one-third of the lake population in Gin and one-quarter in Hamilton.An anomaly between species abundance and sport fishing activities was noted. Crappie (white and black) were never significantly abundant in sampling collections except in August 1973 when they comprised about 5 percent in each lake. However, most of the local fishermen using boats fished primarily for crappie and not largemouth bass, which ranked fourth in abundance in Hamilton and Gin (7 and 6 percent, respectively).

Interaction between fish in the Mississippi River and the oxbow lakes and the influence of river species on lake species composition was demonstrated more clearly in Hamilton Lake, as discussed pre-viously in subsection 2.2.3.2.1.

Additionally, in April and May 1973, the silvery minnow (river species) comprised 17 and 2 percent of the lake population, respectively.

This species was not collected in the June 1972 sample taken after the 1972 spring flood had subsided and Hamilton Lake was separated from the river.A fish kill was observed on August 27, 1973 during electrofishing sampling in Hamilton Lake. The fish, which had been dead about 12 to 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />, numbered about 200 specimens, and were primarily shad, drum and a few catfish. The kill may have been due to low dissolved oxygen levels. Nocturnal oxygen depletion was noted in both lakes. Although similar dissolved oxygen levels occurred in Gin Lake, no fish kill was observed.2.2.3.2.5 Adult Fish Assemblage

-Site Stream A Site stream A drains a small watershed of about 2.8 square miles and is characterized by extreme fluctuations in discharge.

During period of dry weather, the stream had negligible flow and was characterized by isolated pools within the site boundaries.

A significant amount of erosion on the site has generated heavy deposits of loess sediments in the stream bed. Upstream of the site, in the vicinity of fish sampling station 2 (see Figure 2.2-12), significantly/less erosion has occurred, and the stream was characterized by alternating gravel-substrate riffles and loessial-sediment pools.The stream A fish assemblage was characteristic of streams draining loessial bluffs around Vicksburg, Mississippi (Reference 41); fewer species, however, occurred in stream A than in the Vicksburg streams.The intermittent nature of the stream was probably the major factor restricting species composition and population density. Also periodic concentration of fish into pools probably results in heavy predation by the abundant green sunfish (Lepomis cyanellus) and yellow bullheads, effectively reducing population density.2.2-52 GG ER Twenty-one species were collected from stream A. Some of these species were probably not residents, but had entered when river floodwaters backed into the stream basin in March 1973. Species such as largemouth bass, river shiner and warmouth (Lepomis gulosus), normally inhabit the lakes and river in the site vicinity.The gravel-bottom riffle and silt-bottom pool portion of the stream (station 2) contained seven fish species. Bluntnose minnows and green sunfish were numerically dominant.

The population density was estimated (Ref. 33) to be 7230 fish per acre. Estimated stand-ing stock was 79 pounds per acre.An attempt to estimate population density in the lower portion of stream A (station 1) in March 1973 was unsatisfactory because of high water turbidity and heavy sediment deposits in the stream bed. A total of 167 fish, representing 18 species, was removed for the population estimate.

The most abundant species were blunt-nose minnow, green sunfish, longear sunfish (Lepomis megalotis), silvery minnor (a river species) and blackspotted topminnow (Fundulus olivaceus).

Population density was estimated to be 2901 per acre. Standing stock was estimated to be 63.0 pounds per acre. A density estimate less than one-half that at station 2, however, is of suspect accuracy, particularly since the stream is larger and supports a higher diversity of species at station 1.Although it is true that these two factors do not necessarily result in higher densities, in this case the population estimate at station 1 is believed to be low.2.2.3.2.6 Adult Fish Assemblage

-Bluff Ponds There are four small (ca. 0.25 to 0.5 acre) stock ponds and a larger pond (ca. 1 to 2 acre) on the site. The location of these ponds precluded natural population by recruitment from either stream A or B. These ponds were apparently stocked with fish by previous owners. Population estimates were made for two of the ponds. Population density and standing stock were esti-mated by the mark-recapture method (Ref. 34). Confidence limits were placed around these estimates using the method suggested by Adams (Ref. 35).Bluff Pond 1 (ca. 0.5 acre) contained only bluegill and mosquito-fish. The estimates were based on a total catch of 338 bluegill and 51 mosquitofish which weighed a total of 9.02 pounds. Esti-mated population density and standing stock, with confidence limits (95 percent) in parenthesis, were: 2.2-53 GG ER Standing Stock Species Number of Fish (lb./acre)

Bluegill Per acre 4316 115.2 (2214 -5534) (58.9 -147.3)Mosquitofish Per acre 1096 1.092 (410 -2866) (0.407 -2.850)These estimates are equivalent to 5412 fish per acre and 116.3 pounds per acre.The four-to-one ratio of bluegill to mosquitofish indicated an unbalanced population, i.e., one prey (mosquitofish) to four preda-tors (bluegill);

as a result, the bluegill were stunted in growth.Mean total length was 3.2 inches compared to a mean total length of 3.7 inches of 581 bluegill collected in Gin Lake, and 3.8 inches for 49 bluegill from Hamilton Lake.Bluff Pond 2 (ca. 0.25 acre) contained bluegill, mosquitofish, and a few channel catfish. Electrofishing produced 108 bluegill and three channel catfish; the total catch weighed 9.24 pounds.Population density and standing stock estimates, with confidence limits (95 percent) in parenthesis for bluegill were: Standing Stock Number of Fish (lb./acre)

Per acre 1670 41.4 (928 -3867) (23.0 -95.8)The pond also supported a dense population of mosquitofish.

However, most of these fish readily escaped the electrical field, probably because of their small size and the low water conducti-vity (24 pmhos/cm 2). Although their abundance was noted, no attempt was made to estimate their population since it was not possible to efficiently capture the fish.Bluegill in Pond 2 were not stunted in growth, probably because of an abundant food supply (mosquitofish).

The mean total length of the 108 bluegill was 4.3 inches. Although the bluegill popu-lation in Pond 1 appeared stunted in growth, the standing stock was over twice that of Pond 2, largely because of the higher density in Pond 1.2.2-54 GG ER 2.2.3.2.7 Creel Census a. Commercial Fishing Commercial fisheries in the Grand Gulf reach of the Mississippi River have declined significantly in the past 20 years (Ref. 46). Prior to this decline, active fisheries existed. Fish buyers maintained houseboats in the immediate area to purchase fish directly from fishermen.

This practice has been dis-continued and fishermen now transport fish to Vicks-burg or Natchez for sale to fish markets. The number of fishermen has also apparently declined; estimates, however, are only available for the present. The Grand Gulf Nuclear Station Project contacted Mis-sissippi Game and Fish Commission Game Wardens, Salvo Piazzo (Jefferson County) and B. G. Newman (Adams County), and Louisiana Wildlife and Fisheries Commis-sion Law Enforcement Officer, Captain Vance Herring, for information on local fisheries.

Based on these contacts and direct observations of fishing activity in the site vicinity, there may have been 10 to 15 full-time and 30 to 40 part-time commercial fishermen operating between Grand Gulf and Natchez in 1973.During the study period, one full-time fisherman operated from June 1972 through February 1973 in the immediate site vicinity.

Three to five part-time fishermen were also observed.

Creel censuses were obtained from the full-time fishermen on 7 different days in January and February.

The dominant fish in these catches was the bigmouth buffalo; smallmouth buffalo was the next most frequently caught fish. Freshwater drum,. catfishes and paddlefish were also occasionally caught. The average daily catch for all 7 days was 262.5 pounds, worth $131.26 at $.50 per pound (the 1973 price for undressed buffalo and catfish).

This fisherman ceased his activities in early March 1973.b. Sport Fishing Sport fishing and related recreational activities (i.e., camping and boating) in the Grand Gulf vicinity is seasonal in nature. Stage and duration of annual flood-ing has a major influence on these activities.

From November 1972 through March 1973, little or no sport fishing activity occurred.

However, Hamilton Lake, Gin Lake, the Mississippi River, and the Big Black River were used frequently from April through August.2.2-55 GG ER During the period when the 1973 flood crested and receded (April through June), a total of 240 people were recorded on the site water bodies; this was a daily average of 8.6 campers and fisherman (based on 28 observations).

A total of 804 fish (mostly catfishes) were recorded on 15 different days. This was an average daily catch of 53.6 fish and an average catch of 6.1 fish per-angler-day. Boat fishermen were primarily fishing for three species of catfishes (blue, channel and flathead) in floodwaters on the forested bottomland.

Most fishing was done with baited trotlines; catches for fishermen were as high as 100 catfish per night on this gear.Bank fishermen were primarily fishing for sunfishes (e.g., bluegill, crappie and largemouth bass) and catch success was typically low.After floodwaters receded (July and August), sport fishing activities with trotlines occurred primarily along the banks of the Mississippi River. Both bank and boat fishing for sunfishes continued in the lakes.A total of 271 people were recorded on the three water bodies; this was a daily average of 5.9 campers and fishermen (based on 46 observations).

Catch successes were considerably less than those during the flood period. A total of 53 fish were recorded for an average daily catch of 7.6 fish (based on seven obser-vations) and an average catch of 1.3 fish-per-angler-day, a decrease of 86 percent in catch successes.

The decrease was largely due to a sharp decrease in trotline catch success. Trotline catches were periodically very high in the shallow bottomland floodwaters, suggesting possible spawning concentrations of catfishes in these vegetated areas, A maximum of 500 catfish were recorded taken in a 24-hour period by a portion of the fishermen using the flooded bottomlands.

After floodwaters receded, trotline fishing along the river banks resulted in lower catches.Heaviest fishing activity occurred on weekends (including Friday), holidays, and during periods of stable or fal-ling river stage. Observations on fishing pressures suggested fishing success with baited trotlines was related to fluctuations of river stage; catch success apparently increased during periods of stable or fal-ling river stage.Hamilton Lake, Gin Lake, and the Mississippi River (including the Big Black River) received different fishing pressures.

During the flood period, boats were launched at the Gin Lake Landing and at Fort Cobun north of Grand Gulf; Hamilton Lake and Lower Grand Gulf Land-ings (Hamilton Lake outfall) were inaccessible.

During 2.2-56 GG ER that period (March 30 through June 30, 1973), 52 percent of the people were recorded at Gin-Lake, 37 percent at Fort Cobun, and 12 percent enroute to or from these landings.By early July, floodwaters had receded and the Fort Cobun Landing (a soybean field) was dry. Concurrently, the Hamilton Lake and Lower Grand Gulf Landings became accessible by vehicle. During July and August, Gin Lake received the greatest fishing pressure; about 50 percent of all observations were recorded on this lake. Hamilton Lake and the Mississippi River each received about 20 percent of the summer recreation activity.

Similar fishing and recreation pressures existed on the various water bodies during the entire period from March 30 through August 31, 1973.The disproportionate usage of Gin Lake was primarily the result of three factors. During the extended flood-ing, access to Hamilton Lake was difficult and many fishermen used Gin Lake because of its easier accessi-bility. After the flood, the Hamilton Lake Landing, although accessible, required use of a four-wheel-drive vehicle to launch a boat, whereas, the Gin Lake Landing was easily accessible without such a vehicle. Lastly, local fishermen are generally of the belief that Gin Lake affords better fishing than does Hamilton.Boat access to the Mississippi River at Fort Cobun is seasonal and occurs only during very high river stages.Most of the year, fishermen camp at the Lower Grand Gulf landing and launch boats there, or on the river bank revetment south of the outfall. This recreation appears to be a popular activity for citizens of the immediate Mississippi counties and a number of "regulars" frequently use the area. The popularity of this landing may stem from the fact that boat launching sites giving access to the Mississippi River in the Grand Gulf vicinity are limited. The alternatives are two: (a.) St. Joseph, Claiborne County Ferry Landing at river mile 394.2, and (b.) the Karnac Ferry crossing on the Big Black River.Both of these alternative launching sites are about 11 miles by water from Grand Gulf, and are less con-venient and more time consuming to use. than is the Lower Landing.2.2.3.3 Benthic Macroinvertebrates Benthic sampling was conducted at various locations in the Missis-sippi and Big Black Rivers (see Figure 2.2-9) and Hamilton and Gin Lakes (see Figure 2.2-10). River samples were collected 2.2-57 GG ER monthly beginning in September 1972 with a. Shipek sediment sampler;lake samples were collected monthly beginning in October 1972 with a Ponar bottom grab. Starting in January 1973, drifting benthic macroinvertebrate samples were collected near the water surface at two stations in the Mississippi River using a 1-meter diameter planton net (505-micron mesh). Shrimp were also collected in the Mississippi, generally on a monthly basis, using box traps mea-suring 4 x 2 x 1 feet. Crayfish were sampled in the bottomland fields adjacent to'the lakes in June after the 1973 spring flood receded.2.2.3.3.1 Mississippi and Big Black Rivers a. Benthos The Mississippi River at Grand Gulf consists of several macrohabitats (clay bank, backwater, and main channel)within which a characteristic assemblage of benthic macroinvertebrates are found. A diverse assemblage of benthic organisms was collected at various river stations.

Macrohabitats of the river are mainly defined..by current velocity and pattern, sediment type, and water depth. Moreover, since the velocity of the overlying water largely determines the gross type of bottom sub-strate 3 0, current velocity is probably the "master variable" affecting overall benthic distributional patterns in a river system. Principle benthic macro-habitats in the Mississippi River at Grand Gulf are (1) backwaters, (2) steep, clay river banks, and (3)main channel.1. Backwater Backwater macrohabitats in the Mississippi River are located in slow moving, quiet waters on the inside of large bends, in coves on the leeside of sandbars and islands, in the lower reaches of slug-gish tributaries, and in other similar areas. In addition, during flood periods, oxbow lakes are confluent with the main river and become backwaters of the river.Backwater habitats in the Mississippi River system at Grand Gulf (stations 1, 9 and 10; Hamilton and Gin Lakes) are characterized by zero to slow current velocities, relatively shallow waters, and loosely consolidated sediments composed of 85 percent or more silt and clay. Dissolved oxygen near the bottom may become. depleted in warmer months when the water is stagnant.30 Bottom substrate is the main physical characteristic directly influencing the basic type of benthic assemblage in an area.2.2-58 GG ER Backwater areas account for most benthic production of the river and are major feeding and spawning grounds for many river fishes. Benthic assemblages in backwater macrohabitats typically consist of dipteran larvae (mainly chironomid and phantom midges), tubificid worms and, to a lesser extent, bivalves.

Considerable variation occurs in the relative abundance and taxonomic composition of backwater benthos with respect to these dominant groups. Benthic population densities and standing stocks in backwater macrohabitats are relatively large and fluctuate temporally.

The mud flat at station 1 is located in the lee of a towhead on the west bank of the river approxi-mately 5 miles downstream of the Lower Grand Gulf Landing and is bordered to the east by the main river channel. Station 1 was the largest backwater habitat of this type in the study area and is approximately 120 acres in surface area.The benthic macroinvertebrate assemblage inhabit-ing the organically rich silt-clay sediments at station 1 was numerically dominated (78 percent)by tubificid worms; chironomid larvae (dipteran) composed most of the remaining benthos. Total benthic densities ranged from a minimum of 540 organisms/m 2 in August 1973 to a maximum of 7670 organisms/m 2 in June 1973. Although numerous fluctuations occurred, a general increase in benthic numbers occurred from September 1972 through June 1973. In July and August, however, total benthic density decreased.

Benthic dry weight standing stock ranged from a low of 311 mg/m 2 in August 1973 to a high of 5543 mg/m 2 in April 1973. Tubifi-cid worms and,. because of its larger size, the burrowing mayfly (Hexagenia) codominated standing stock on the mud flat from September 1972 through June 1973. However, in July and August, tubifi-cids, leeches, and bivalves were dominant organisms.

A general increase in modal population size of Hexagenia was evident for the study period. The importance of the backwater at station 1 as a feeding ground for fishes is readily apparent con-sidering that the estimated total dry weight stand-ing stock of benthic macroinvertebrates on this mudbar was roughly 3 tons in April, the month of maximum standing stock.Lower reaches of the Big Black River, particularly near its mouth, may be classified as a backwater habitat of the Mississippi River system. In con-trast to conditions at station 1, the benthic 2.2-59 GG ER macroinvertebrate assemblage at station 10 (1/4 mile up the Big Black from its mouth) was composed mainly of dipteran larvae (principally chironomids) from September through March; subsequently, bivalves and tubificids were numerically dominant.

The spring decrease in chironomid numbers probably reflected adult emergence.

Total benthos density increased from lows in the fall and winter to spring maxima in March and June. Total densities ranged from 192 organisms/m 2 in September 1972 to 3955 organisms/m 2 in June 1973.Standing stock of benthos in the Big Black peaked twice during the preconstruction study period: October 1972 at 4096 mg/m2-and July 1973 at 11,510 mg/m 2.Standing stock values were comparably low from September 1972 through May 1973. Bivalves and tubificids composed most benthic standing stock in the Big Black. Dipteran larvae were important in September and December, and mayfly (Hexagenia) biomass was abundant in November.Like the mud flat at station 1, the Big Black is probably an important feeding ground for bottom-feeding fish since the benthos of this tributary is comparably productive and abundant.Benthos in the chute on the leeside or western side of Middle Ground Island (station 9) was variable, being alternately backwater and main channel macrohabitats.

Spur dikes at the upstream end of the chute divert most river flow to the eastern side of the island during low-flow periods and, consequently, silt-clay sediments build up on the chute bottom during these times. From September through December, low-flow conditions existed and there was little current at station 9.The resulting mud substrate contained populations of benthos during the fall which increased from 75 organisms/mz in September to 505 organisms/m2 in December.

Benthos at station 9 was mainly chironomid larvae. Benthic diversity, however, increased at station 9 from two taxa collected in September to 16 taxa collected in November.This marked rise in diversity can probably be attributed to colonization of the bottom by drift-ing benthic species carried into the chute by rising floodwaters in November.

By January, however, river floodwaters had risen to the point that current velocity in the chute became strong enough to scour the bottom free of silt, leaving a sand substrate.

Consequently, benthic popula-tions disappeared in January and, as a result of 2.2-60 GG ER prolonged flooding, did not become reestablished until July or August 1973. However, in August, as mud built up on the chute bottom due to reduced current velocities, benthos became reestablished at a total density of 17 organisms/m 2.2. Clay bank Banks of the Mississippi River are steep and generally composed of various types of consolidated silt and clay. Clay bank stability varies greatly depending on local soil geology, amount and type of terrestrial vegetation, and degree of scouring by currents.

Generally, in areas of stable banks, large populations of benthic macroinvertebrates (mainly mayflies) were present, whereas in reaches where the bank was constantly eroding, macroin-vertebrates were scarce or non-existent.

Exten-sive removal of stable clay bank habitat in an area by revetment and other river channelization programs causes significant decreases in biologi-cal production.

Clay banks of the Mississippi River at Grand Gulf were sampled in four locations, stations 2, 3, 5 and 6 (see Figure 2.2-9). The bank environment at stations 2 and 6 had high current velocities and was comparatively unstable.

No benthos was collected at station 2 in September and October 1972, and this station was not sampled after November.

Similarly, no organisms were collected at station 6 until March when this station was moved approximately 1/2 mile downstream to a less severe area (station 6). Subsequently, densities of 25, 45 and 5 organisms/m 2 occurred on the bank at station 6 in March, June and August, respect-ively. These consisted of tubificids, the midges Cryptochironomus and Chaoborus, and the mayfly Pentagenia.

The clay bank at station 5 supported benthic popu-lations of moderate abundance (35 to 125 organisms/m 2)from September through December, 1972. In January, 1973, however, the substrate at station 5 changed from clay to sand as a result of sediment transport by floodwaters, and no benthic organisms were present from January through March. Some coloni-zation occurred in April and May (5 and 45 organisms/m 2), but benthic concentrations dropped to zero again in June, July and August. A variety of organisms including mayflies, bivalves, chir-) onomids, tubificids, and amphipods were collected at station 5.2.2-61 GG ER In-contrast to other clay bank areas, the bank in the eddy current at station 3 contained large populations of the burrowing mayflies Pentagenia and Tortopus.

Respiratory tubes of these mayflies gave the substrate a "honey combed" appearance.

The abundance of Pentagenia and Tortopus made the bank at station 3 one of the most productive habitats for benthos in the river. Benthic densi-ties decreased regularly from a high of 1467 organisms/m 2 in October 1972 to a low of 20 organisms/m 2 in June 1973. Densities began to increase again in July to 875 organisms/m 2 in August. The mayfly Tortopus reappeared, for the first time since November 1972, in July and August 1973 with densities of 50 and 255 organisms/m 2 , respectively.

Standing stock levels showed a temporal trend similar to that of densities with a peak of 9073 mg/m 2 in October and low of 16 mg/m 2 in June.The pronounced decrease in mayfly abundance from February through June may be associated with natural mortality, predation, adult emergence, or a combination of these and other factors. Adult mayflies Pentagenia and Tortopus were observed at Grand Gulf from June through early October 1973.Pentagenia size increased during the year. Size structure of the population exhibited modal increases from the 5 to 10 and 10 to 15 mm total length (TL) size classes in September and October 1972, to the 15 to 20 mm (TL) class for November through April, and to the 20 to 25 mm (TL) class in May and June. Mean individual dry weight of Pentagenia also increased from 2.39 mg in September 1972 to 11.6.4 mg in June 1973, and then decreased to 1.73 mg in August. Recruitment of young-of-the-year organisms was evident in the summer, with subsequent growth of individuals to maturity in the spring.3. Main Channel The river channel is the dominant benthic macro-habitat in the Mississippi River in terms of area.Strong currents and coarse sand-gravel sediments at stations 4 and 7 are characteristic of the main channel environment.

Thirty-six benthic samples collected at main channel stations in September, October, March, June, July and August contained no macroinvertebrates.

This large area is, there-fore, considered to have virtually no benthos.2.2-62 GG ER In summary, benthic sampling in the Mississippi River from September 1972 through August 1973 showed that the most productive areas for benthos were the backwater at station 1 and the clay bank at station 3. Backwaters in the chute on the western side of the Middle Ground Island (station 9), except after January, and in the Big Black River (station 10) were also important habitats for benthos, although to a lesser degree than at stations 1 and 3. Areas of clay bank other than.at station 3 (i.e., stations 2, 5, 6 and 8) had a depauperate benthic fauna. The main channel environment was apparently devoid of macroinver-tebrates.b. Drifting Benthic Macroinvertebrates Benthic macroinvertebrates in the Mississippi River and adjacent backwaters regularly exhibit the phenomenon known as benthic drifting.

Mean daily benthic drift intensity in the river at stations 3 and 6 was low in January (0.1 organisms/m 3), rose to intermediate levels (0.5 organisms/m

3) from March through May, increased threefold to a pronounced peak of 2.3 organisms/m 3 in early June, and decreased signifi-cantly in July. Nocturnal concentrations of drifting macroinvertebrates were typically

1.5 times

greater than diurnal concentrations.

Mean nocturanl densities of drifting benthos at stations 3 and 6 averaged 1.6 organisms/m 3 , ranging from 0.2 to 3.7 organisms/m 3.In contrast, diurnal densities at both stations average only 0.5 orianisms/m 3 and ranged from 0.1 to 1.6 organismsm..

Chironomid pupae and larvae of the phanton midge Chaoborus composed a majority of benthic drift; coleop-teran larvae, mayfly larvae, and amphipods were also common. A total of 96 taxa of macroinvertebrates were collected in drift samples. Drift intensity was greatest during flooding when river water flowed across back-water areas such as oxbow lakes and the lower reaches of tributaries.

It is apparent that the primary source of drifting organisms was not the river channel but these backwaters.

The fact that drift intensity declined markedly within a few days after Hamilton and Gin Lakes became separated from the river in late June supports this hypothesis.

Benthic drift in the.Mississippi River may be generally classified as the-"catastrophic" type in which organisms are physically torn from their normal habitat by strong 2.2-63 GG ER currents or other physical forces (Ref. 52). A"behavioral" drift component was also evident from the significant difference in diurnal and noctural drift intensities.

For example, Chaoborus is benthic in the daytime but migrates upward into thewater column at night. This phantom midge was numerically dominant in Hamilton and Gin Lakes in the fall. As the currents of rising floodwaters increased during late fall and early winter, populations of Chaoborus were depleted because individuals were continually swept from lakes into the river during their daily nocturnal migration into surface waters.c. Shrimp River shrimp (Macrobrachium ohione) were seasonally abundant in the Mississippi River at Grand Gulf where they were collected mainly along the river banks. A few shrimp were collected in trawl samples from the open channel. Shrimp catches along the river bank at stations 3 and 6 were moderate in September 1972, but increased to a fall peak in October. Except for one-specimen in March, no shrimp were collected from Novem-ber 1972 through April 1973. Catches again peaked in August to the preconstruction study-period maximum.Catch per unit effort values ranged from 0 to 22.3 shrimp per trap per day. The decline in shrimp catches in November occurred concurrently with a sharp drop in river water temperature to about 7.5 C. Likewise, the spring rise in catches occurred simultaneously with a sharp increase in water temperature to above 20 C. The decline in winter shrimp catches is not believed to reflect a general reduction in population size, but probably results from decreased activity due to cold water temp-eratures.

A few shrimp were taken in beach seine hauls, in hoop nets, electrofishing equipment, and from the intake screens at MP&L's Baxter Wilson Steam Electric Station in Vicksburg during winter months.One gravid shrimp was collected in early September 1972, but none were subsequently captured until the next May.During May and June all females were gravid. In August, females composed 97 percent of the catch but only 5 percent of the females were gravid. These data strongly suggest that river shrimp spawn in a fairly discrete period in late spring through mid-summer.

2.2.3.3.2 Hamilton and Gin Lakes a. Benthos Hamilton and Gin Lakes are relatively shallow, varying from 6 to 30 feet deep depending on the flood stage of the river. Lake bottom sediments are loosely consoli-2.2-64 GG ER dated and composed of over 95 percent silt and clay-size particles, and the organic content of lake sedi-ments is high. Dissolved oxygen depletions occurred near the bottom in the summer of 1973.Benthic macroinvertebrate assemblages of the oxbow lakes were similar to those of backwater areas in the river proper. Larvae of the phanton midge Chaoborus and various genera of chironomid midges (e.g., Coelotanypus, Procladius, Cryptochironomus, Pentaneura and Tanypus) numerically dominated the lakes in the fall and winter; tubificid worms and bivalves were spring dominants.

Several species of aquatic inverte-brates not collected by the bottom grab were also common in the lakes. These included the large unionid mussels Carunculinus, Anodonta and Lampsilus, and the large snails Campeloma and Viviparus which occurred sporadically in fairly dense clusters in shallow waters along the lake shore. In addition, whirligig beetles (Gyrinus) and water striders (Notonectidae) occurred frequently on the lake surface. The crayfish Procambarus and grass shrimp Palaemonetes kadiakensis were common-in shallow nearshore waters.Total benthic density exhibited little temporal varia-tion throughout the preconstruction study period in Hamilton Lake. Total density ranged from 1270 to 2920 organisms/m 2.Temporal fluctuations in benthic density were somewhat more pronounced in Gin Lake.Benthic macroinvertebrate abundance peaks in Gin occurred in late fall-early winter, spring and mid-summer.

The study-period minimum occurred in late winter. Total benthic density ranged from 987 to 3242 organisms/m2 in Gin.In contrast to benthos density, the standing stock of macroinvertebrates in both lakes fluctuated signifi-cantly on a temporal basis. Peaks in benthic standing stock were observed in each lake during the spring;biomass had steadily increased from fall minima to spring maxima. Declines in standing stock began in early summer and continued through late summer. Stand-ing stock levels ranged from 252 to 3886 mg/m 2 in Hamilton and from 162 to 3489 mg/m 2 in Gin. Bivalves generally dominated benthic standing stock of both lakes during the spring maximum, but diptera and tubificids were generally most abundant in other months.b. Crayfish An abnormally abundant population of crayfish was pre-sent along the lakes during the spring of 1973. As floodwaters began to recede in June, large numbers of 2.2-65 GG ER crayfish chimneys were observed in the previously inundated fields adjacent to Hamilton and Gin Lakes.The density of active chimneys in seven bottomland fields on and immediately adjacent to the site ranged from 680 to 9110 per acre and averaged 2931 chimneys per acre for all fields combined.

As the floodwaters receded from the fields and the subsoils began draining, crayfish were observed to construct new chimneys closer to the waters edge, abandoning their existing chimneys.Numerous adult crayfish of the genus Procambarus (pos-sibly P. acutus acutus) were observed at night in the fields along the lakes and were collected in commercial quantities by local residents.

Crayfish were not as abundant in the site area, however, as they reportedly were along the river near Vicksburg.

Minnow seine hauls in ditches and other shallow floodwater areas along the lakes in June contained large numbers of small (0.5 to 2.0 inches total length) juvenile Procambarus.

These juveniles were probably hatched in the early spring.The abnormally successful year for crayfish can probably be attributed to the prolonged presence of exceptionally large areas of idea backwater habitat.2.2.3.4 Plankton Plankton sampling was conducted at various locations in the Mis-sissippi and Big Black Rivers (see Figure 2.2-9) and Hamilton and Gin Lakes (see Figure 2.2-10) with various frequencies (monthly to semimonthly) and intensities from September 1972 through August 1973. Replicate river samples were collected at stations 1 through 10 prior to December 1972, and subsequently at stations 1, 3, 6 and 10. Throughout the study, sampling was not standard-ized at specific times of the day because of the logistic problems associated with the sampling of four water bodies. Zooplankton densities were determined from samples obtained with a Clarke-Bumpus sampler (No. 10 mesh net). Phytoplankton densities were determined from whole-water sample. Zooplankton standing stock and phytoplankton standing crop were determined using their den-sities and biovolume/biomass estimates.

Beginning January 1973, an additional measure of phytoplankton standing crop was obtained from chlorophyll-a analysis.2.2.3.4.1 Introduction Plankton are organisms that live adrift in nearly all bodies of-water from the smallest ponds, to rivers, to the largest lakes and oceans. Plankton may be divided into two broad, distinctly different groups: phytoplankton and zooplankton.

Phytoplankton are typically microscopic, photosynthetic, producer organisms that 2.2-66 GG ER form the base of the aquatic chain. Aside from their importance as food for larger organisms, phytoplankton are responsible for producing much of the oxygen utilized by all other aquatic life.Oxygen is produced as a by-product of the photosynthetic process in which carbon dioxide is converted into sugar, the basic food-producing function of phytoplankton.

The small size of phyto-plankton is countered by their great reproductive capability (whi*ch frequently exceeds one division per day). Typical subdivi-sions of freshwater phytoplankton include blue-green algae, green algae, euglenophytes, and diatoms.Zooplankton are also usually microscopic but are more structurally complex consumer organisms that obtain their nutrition by con-suming other zooplankton, phytoplankton, bacteria, and/or detritus.Excluding protozoans (which typically have rapid reproductive rates), zooplankton reproductive rates are much lower than those of phytoplankton (zooplankton development time usually ranges from a few days to a few weeks). As a consequence, total zooplankton densities and frequently,.biomass are also much lower in a body of water. Like phytoplankton, zooplankton are themselves important food items for larger aquatic consumers such as fish and aquatic insects. Typical freshwater zooplankton sub-groups include protozoans, rotifers, cladocerans, and copepods in addition to the larvae of usually nonplanktonic organisms such as insects and other invertebrates.

A large river, in contrast with most lakes and oceans, is not a particularly favorable place for an indigenous plankton assemblage, mainly because of the continual, fast, turbulent flow. Plankton by their drifting characteristic are at the mercy of the turbu-lence. Generally, lakes are not subject to such continual tur-bulence. Consequently, typical lake plankton are often not well adapted to survival in the Mississippi River with its continual high turbidity and turbulence.

The photic zone 3 is very shallow in the Mississippi.

Phytoplankton production is therefore limited;consequently, zooplankton production may also be limited. Much production is tied up in the adventitious plankters that have been flooded out of lakes and backwater areas. These include many crustaceans and larval insects in addition to other rotifers, protozoans, and algae.The river carries plankton far from its point of origin in a few days. Generally speaking, plankton at any given place in a river may be assumed to have originated upstream in tributary streams, lake, and backwater areas. Consequently, in a river, a true drifting community of self-reproducing organisms has no chance to develop except in backwater areas.The interrelationship between the Mississippi River and its back-waters in the Grand Gulf region, particularly the two oxbow lakes, Hamilton and Gin and its tributary the Big Black River, is well 31 The zone with sufficient light for photosynthesis.

2.2-67 GG ER illustrated in the plankton.

During periods of low flow (Sept-ember through early November 1972 and July through August 1973), plankton associations were distinct in the Mississippi River, Big Black River, Hamilton Lake, and Gin Lake. When the Mississippi River flooded, river plankton strongly influenced plankton density and biomass of the two oxbow lakes and the Big Black River near Grand Gulf.Except for short periods from late November 1972 through June 1973, the flooding Mississippi continually flushed the two oxbow lakes and backed into the Big Black River. As the flushing began in November, lake species composition and abundance changed dramati-cally. Mississippi River plankton replaced that of the lakes, and lake plankton abundance declined more than an order of magnitude to values comparable to those of the Mississippi.

Plankton associations in all four water bodies during much of the 8-month flood period were similar to each other, producing nearly identi-cal taxa lists, which reflect the sum of various physical-chemical influences on river plankton upstream.

Temporal changes in plankton density and biomass, moreover, were also similar, reflecting these same upstream influences.

The Mississippi River influenced the plankton of the other three water bodies far more than the reverse. The effect of the Big Black River, for example, was particularly noticeable on the plankton of the Mississippi during the preconstruction study period only during lowest flows in September 1972 and August 1973. In September, the cladoceran Moina micrura dominated the Big Black zooplankton (97 percent of numeric1Valensity) but was absent from the Mississippi above the confluence of the two rivers. Downstream from the confluence, however, M. micrura was present (although only at a density of less than-5 percent of that in the Big Black).Again in August 1973, M. micrura dominated the Big Black (4222 organisms/mr) but was ?ar less numerous in the Mississippi (84 organisms/m 3).*The lakes, of course, contributed their own plankton to the Mis-sissippi when they were flushed for the first time in mid-November.

The comparative influence of the lake plankton on a volume of water as great as the Mississippi is quite small: for example, on November 7, 1972, a volume of water equal to the total volume of both lakes (25 million cubic feet) flowed past Grand Gulf in about 40 seconds with a river flow rate of approximately 0.63 million cfs.2.2.3.4.2 Mississippi' River Mississippi River zooplankton and phytoplankton exhibited sharply different temporal patterns of abundance during the preconstruc-tion study period. Zooplankton density and standing stock dis-charges were substantially lower from September through January 2.2-68 GG ER than from February through early June and were again lower from late June throughAugust.

Phytoplankton density and standing crop discharges, on the other hand, peaked at a study-period maximum in early November and exhibited another peak in late spring.They exhibited low values in the winter and summer.Mississippi River zooplankton density ranged over two orders of magnitude during the study period from 367 to 44,828 organisms/

m 3 , while zooplankton standing stock 3 2 ranged less broadly from 10 to 172 mg/m 3.Discharge density of zooplankton organisms was relatively constant for the period September 1972 through February 1973. During the same period, however, discharge stand-ing stock rose gradually but steadily.

Although discharge density peaked abruptly in mid-March, 1973, standing stock did not peak until three weeks later. As was frequently the case, the numer-ically dominant organisms contributed relatively little to the standing stock. Thus in mid-March, the small, stalked, river protozoan Carchesium sp. was a 93 percent numerical dominant and contributed substantially to the highest numerical zooplankton density measured in any of the four water bodies (44,828 organisms/

m 3). In terms of standing stock, however, Carchesium sp. was insignificant, comprising less than 4 percent in mid March. In fact, discharge standing stock peaked in early April at a value more than twice that of mid-March.

Moreover, Carchesium sp. had nearly disappeared by early April. Total standing stock reached its peak for the study period in early June (172 mg/m 3). During the study period, and particularly for early April and early June maxima, various Cladocera (Daphnia spp., Ceriodaphnia sp. and Bosmina longirostris) and both cyclopoid and calanoid copepods dominated the standing stock. Of the 46 Mississippi River zoo-plankton taxa identified during the study period, Bosmina long-irostris was particularly characteristic of the Mississippb-eing one of the three most abundant river zooplankters on 10 of 16 sampling dates.A colonial rotifer, Conchiloides sp.3 3 , was a river dominant during the spring, comprising at least 30 percent of river zoo-plankton densities in April and May 1973. Previously, Conchi-loides sp. had been a dominant zooplankter observed in the lakes prior to flooding.

The role of the river in introducing taxa such as Conchiloides sp. into the lakes is discussed in subsection 2.2.3.4.4.

Mississippi River phytoplankton abundance experienced both a fall and a spring bloom, a typical occurrence in many bodies of water.Phytoplankton discharge density and standing crop were highest 32 All biomass values are biovolumes that have been converted to wet weights.Conchiloides sp. is another small, frequently numerically abundant taxon which contributed relatively little to standing stock.2.2-69 GG ER in early November (respectively, 7.6 x 1015 cells/minute and 4440 kg/minute), were much lower from December through early May (lowest values of the study period were approached in mid-March -0.9 x 1015 cells/minute and 560 kg/minute), were higher again in early June, and were low in July and August.Although density and standing crop changed greatly during the study period, the actual species composition changed relatively little. The dominant taxa were centric diatoms. Invariably, either Melosira spp. or Cyclotella spp. dominated the numerical density. In addition, other centric diatoms (Stephanodiscus spp.and Coscinodiscus sp.), pennate diatoms (Asterionella sp., Navicula spp. Nitzschia spp., and Synedra spp.), and euglenoid (Trachelomonas spp.) were frequently important in both numbers and standing crop. An additional 49 phytoplankton genera were identified from the Mississippi during the preconstruction study period. Only rarely did any of these 49 become one of the three dominants.

2.2.3.4.3 Big Black River Big Black River plankton in the vicinity of Grand Gulf was at times quite distinct from that of the Mississippi River and at other times, indistinguishable.

When the Mississippi River stage was low, the Big Black generally had its own characteristic plank-ton. When the Mississippi River stage was high, the Mississippi backed far into the Big Black and, consequently, influenced plankton composition near the mouth of the Big Black.During the low-water periods (September 1972 and August 1973), the cladoceran Moina micrura dominated Big Black zooplankton density and standing stock. During these same two months, the Mississippi River had comparatively insignificant populations of M. micrura and, in fact, total zooplankton abundance was several Eimes lower in the Mississippi than in the Big Black.During high-river stages (November 1972 through June 1973), tem-poral zooplankton fluctuation patterns of the two rivers were very comparable, suggesting the strong influence of the flooding Mis-sissippi on its tributaries.

During that time, species composi-tion was also quite comparable.

From November through June, almost invariably at least two of the three dominants were the same for both rivers on a given sample date even though densities may have differed.In mid-September 1972, Big Black zooplankton exhibited its highest standing stock of the preconstruction study period (332 mg/m 3), with 99 percent due to Moina micrura. Three weeks later, total density and standing stock approached their lowest values for the year (respectively, 314 organisms/m 3 and 11 mg/m 3). From early fall through winter, density and standing stock rose slowly 2.2-70 GG ER and steadily.

Density peaked for the preconstruction study period in mid-March (9485 organisms/m

3) and again in early June (9302);standing stock peaked in early June, declined sharply by mid-June, but peaked again in July and August. Both the late spring and summer peaks were lower than the previous September peak.Big Black River phytoplankton density and standing crop were dis-tinctly different than those of the Mississippi from September through January. Big Black phytoplankton abundance was much lower than that of the Mississippi from September through December.

In early January, however, Big Black phytoplankton density and standing crop were at their maximum levels (respectively, 2031 million cells/m 3 and 1362 mg/m 3) for the study period and were much higher than those of the Mississippi.

At that time, the high Mis-sissippi River stage caused a reduction of flow in the Big Black River for the first time in the study period. This produced the appropriate conditions for a peak in Big Black phytoplankton.

When the Mississippi River backed into the Big Black from February through June, the Big Black River phytoplankton density, standing 3 4 crop and composition, closely paralleled those of the Mississippi By mid-July, after the Mississippi stage had fallen, the two rivers again had distinct phytoplankton assemblages.

While the Missis-sippi remained dominated by its characteristic diatoms, the Big Black was dominated by green algae, blue-green algae, and euglenophytes.

Over the entire study period, phytoplankton abundance in the Big Black averaged the lowest of the four water bodies. Big Black phytoplankton density ranged from 199 to 2031 million cells/m 3 , while standing crop ranged from 70 to 1362 mg/m 3.2.2.3.4.4 Hamilton Lake The plankton composition and abundance in Hamilton and Gin Lakes are greatly affected by the frequency and duration of regular flooding by the Mississippi River. When Hamilton and Gin Lakes are separated from the Mississippi, they develop distinct plankton assemblages such as those which occurred from September through early November 1972 and in July and August 1973. When the lakes are flooded (essentially flushed), however, the lake plankton assemblage is closely related to. that of the Mississippi; this condition occurred from late November 1972 through June 1973.Occasionally, for brief periods during the flood season, the lakes may be cut off from the river. Consequently, they may develop a distinct plankton assemblage for a short time such as that which occurred in early March 1973.34 Except in mid-March, when the Mississippi fell and no longer backed into the Big Black but still retarded Big Black flow.At that time, a distinct phytoplankton assemblage was observed in the Big Black.2.2-71 GG ER In the fall, Hamilton Lake zooplankton was dominated by a small rotifer, Conchiloides sp., and a cyclopoid copepod, Ergasilus sp., both also characterized Gin Lake zooplankton in the fall. Total zooplankton density and standing stock were generally higher in the fall prior to flooding, lower from November through February, Higher again from March through May, and lower again following renewed separation from the Mississippi from June through August 1973.Hamilton Lake surface zooplankton density during the study period ranged over an order of magnitude from 369 to 19,060 organisms/m 3 , while standing stock ranged from 7 to 417 mg/m 3.Mid-depth density and standing stock ranges were, respectively, 1787 to 23,072 organisms/m 3 and 44 to 235 mg/m 3.Substantial differences in surface and mid-depth density on a sampledate were occasionally measured, particularly in the spring;however, only a few consistent patterns in total density were evi-dent. For instance, in early March 1973 both surface total den-sity and standing stock were more than 75 percent larger than mid-depth values. All major taxa (e.g., rotifers, copepods, and cladocerans) had higher density and standing stocks at the sur-face than at mid-depth.

Total standing stocks, moreover, were also higher at the surface in late March, late April, and early and late May. In early April, mid-May and mid-June, however, total standing stock was, respectively, 13, 17 and 38 percent lower at the surface than at mid-depth.

This relationship held for total density through March and April; in May and June, however, surface density was the greater when surface standing stock was the lesser.The pattern of vertical distribution was more pronounced for Cladocera than it was for total standing stock. For most of the sampling dates, the dominant Cladocera had higher numerical den-sities near the surface than at mid-depth.

Daphnia spp., for instance, were seven times more numerous in early March at the surface than at mid-depth.

In late March and late April, Bosmina longirostris were nearly three times more numerous at the surface than at mid-depth.

Vertical distribution in zooplankton has been attributed to various factors such as light, gravity, thermal gradients, and chemical gradients (Ref. 53). Distinct diel vertical plankton movements have been noted in many bodies of water that are typically deep, nonturbulent and not particularly turbid. It has been demonstrated that cladocerans, in particular, migrate away from bright light (Pef. 53). Consequently, in many lakes, Cladocera are more concentrated at deeper levels during the day than near the sur-face.Hamilton Lake was shallow in early March 1973, but relatively deep from April through June 1973. Flooding of the lakes by the river produced turbulence and quite turbid conditions; these conditions 2.2-72 GG ER hindered the detection of vertical plankton migration.

A vertical stratification in Cladocera, however, was often observed; they were generally found to be more concentrated at depths of 3 feet than at 10 feet. Hutchinson (Ref. 53) reports, however, that some plankters will migrate toward a dim light. It is likely that such dim-light-conditions prevailed at the 3-foot depth in the turbid Hamilton Lake water, perhaps explaining the higher concentration of Cladocera near the surface.The overall temporal pattern of abundance, whether surface or mid-depth, was characterized by abrupt changes. These changes were usually associated with large fluctuations in river stage.When the lake was first flooded in November 1972, following a sharp 20-foot rise in river stage, the preflood numerically dominant Conchiloides sp. abruptly decreased more than an order of magni-tude. From November 1972 through February 1973, Hamilton Lake and the Mississippi shared a similar zooplankton association (cyclopoid copepods, Carchesium sp., Asplanchna sp., Brachionus spp. and Bosmina longirostris).

In early March, however, when the lake was briefly cut off, cyclopoid copepods and Daphnia spp. increased very sharply in a short period and produced the highest standing stock measured in Hamilton Lake during the study period (417 mg/m 3).With renewed flooding in mid-March, lake standing stock once again equilibrated with that of the river. At the same time, Conchiloides sp., which had become the river dominant (from an upstream source), also invaded the lakes. Conchiloides sp. had been the lake dominant in the fall (50 to 80 percent of numerical density in September and October).

Conchiloides sp. again dominated the lake zooplankton from March through June. This occurrence strongly suggests the influence of Mississippi River plAnkton on the plank-ton composition of associated oxbow lakes. If the lakes had been severed from the river in April or May 1973, Conchiloides sp. and other taxa present would have been the innoculum for a renewed lake zooplankton succession.

3 5.Merely being the dominant taxon in the innoculum, however, would not necessarily suggest continued dominance during succession.

Following separation from the Mis-sissippi River, Hamilton Lake zooplankton in July and August, in fact, lacked any Conchiloides sp. and was dominated, respectively, by Diaphanosoma brachyurum and Brachionus angularis.

By the end of August, zooplankton density and standing stock were both at study-period lows.Hamilton Lake phytoplankton was substantially more abundant from September through November and then again in July and August than 35 Lake plankton typically undergo a change in species composition throughout the year. Such a succession in a nonflooding lake may be quite similar from year to year. In flooding oxbows, however, species succession is necessarily influenced by those species present when annual flooding ceases.2.2-73 GG ER for the rest of the preconstruction study period. Near-surface 3 6 total phytoplankton density ranged over two orders of magnitude from 192 to 40,2L49 million cells/m 3 , while standing crop had a similarly broad range from 99 to 27,893 mg/m 3.Prior to flooding, the important taxa numerically were a small desmid, Selenastrum Westii, and the same two centric diatom genera that dominated the Misssissippi, Melosira spp. and Cyclotella spp.In late October, two euglenoids, Euglena sp. and Trachelomonas sp., experienced a large bloom and produced the largest measured stand-ing crop of any of the four water bodies. At the same time that the Hamilton Lake euglenophyte bloom was measured, there was a concurrent sharp decline (66 percent) in total zooplankton stand-ing stock and Ergasilus sp. in particular.

It is possible that the euglenophyte bloom caused a detrimental effect on the Ergasilus sp. population in Hamilton Lake, conceivably by depletion of oxygen.After the lake was flooded, total phytoplankton density and stand-ing crop declined dramatically and remained low through June with only relatively minor fluctuations.

Centric diatoms, as in the Mississippi River, usually dominated the flooded lake: occasional subdominants included Nitzschia spp., Trachelomonas spp., Synedra spp. and colonial flagellates.

By late July, the lakes had again separated from the Mississippi and developed high phytoplankton densities comparable to those which existed prior to flooding.

Selenastrum Westii was again the numerical dominant, while Cyclotella spp. and Melosira spp.continued standing crop dominance.

At the end of August, Hamilton Lake total phytoplankton density was at its highest value for the study period. Selenastrum Westii was an 82 percent numerical dominant while a green colonial flagellate and Trachelomonas sp.shared standing crop dominance.

2.2.3.4.5 Gin Lake Gin Lake plankton density and biomass prior to November 1972 flood-ing were distinct from those in the other three water bodies. The species composition of Gin Lake plankton, moreover, was also dis-tinct from the two rivers. Species compositions of the two lakes, however, were quite similar. Dominant zooplankton taxa of both lakes were Conchiloides sp., Ergasilus sp. and Diaphanosoma brachyurum.

Dominant phytoplankton taxa of both were Selenastrum Westii, Melosira spp., Cyclotella spp., Euglena sp. and Trachelo-monas spp.Both before and after flooding occurred, Gin Lake and Hamilton Lake zooplankton assemblages exhibited similar abrupt changes in density, standing stock, and species composition.

For example, between 36 Mid-depth density and standing crop are discussed only if they differ significantly from near-surface values.2.2-74 GG ER early and late November 1972, total Gin Lake Zooplankton density.and standing stock declined 86 and 92 percent, respectively.

During that period, the Mississippi rose over 20 feet, flooded the lakes and decimated the established Conchiloides sp. and Ergasilus sp.populations.

Another abrupt change occurred between late February and early March 1973. Total surface zooplankton density and stand-ing stock increased over 12 times and 17 times, respectively.

During that period, the river stage had-dropped sharply and the lakes were briefly cut off. Cyclopoid copepods and Daphnia spp.were the dominants.

Following renewed flooding, total standing stock, in particular, declined sharply. Zooplankton density continued to fluctuate through the spring, achieving a maximum numerical density in early June (35,672 organisms/m

3) before declining by mid-June.

July and August zooplankton densities maintained relatively low values. In fact, in August, Gin Lake total zooplankton density was at its lowest for the study period.In general, both zooplankton density and standing stock peaked at higher values in Gin Lake than in Hamilton Lake. For example, Gin Lake surface density peaks in early October, early March and early June were, respectively, 41, 27 and 27 percent higher than those in Hamilton Lake. Gin Lake surface standing stock peaks for the same dates were, respectively, 34, 8 and 13 percent higher than those in Hamilton Lake. In fact, comparison of the temporal patterns of total standing stock in both Hamilton and Gin Lakes reveals that the two fluctuated in concert. The pattern for both lakes, whether up or down, was identical on 14 of 16 sampling dates.Gin Lake phytoplankton density and standing crop were several fold greater before the river flooded than at any time during flooding from December 1972 through June 1973. As happened in Hamilton Lake, Gin Lake phytoplankton density and standing crop increased in July and August to high values comparable to those of early fall 1972. Contrary to the case for zooplankton, Gin Lake phyto-plankton density was not consistently greater than that of Hamil-ton Lake.2.2.3.5 Lake Periphyton and Macrophyton 2.2.3.5.1 Periphyton Stands of dead trees occur in the waters along the western and northern perimeters of Hamilton and Gin Lakes. The submerged surfaces of these trees provide substrate for growth of attached algae and invertebrates (periphyton and Aufwuchs).

Fall 1972 periphyton, prior to flooding, was dominated by thick mats of filamentous green algae, Rhizoclonium sp. Associated with the Rhizoclonium filaments were numerous species of pennate diatoms (Navicula spp., Cynnbella spp., Gomphomena spp.) and the filamen-tous centric diatom Melosira spp. Dominant fauna in the fall associated with the Aufwuchs were nematodes (Nemata), leeches (Hirudinea) and flatworms (Platyhelminthes).

2.2-75 GG ER Periphyton was substantially reduced during the winter partly because the water level fluctuated greatly. During April and May 1973, the filamentous diatoms Melosira granulata and Melosira distans dominated the periphyton which at that time was located in the upper branches of living trees surrounding the lakes. Most of the dead tree substrates were totally submerged and beneath the photic zone.In July the lakes returned to their pre-flood levels, and the dead tree substrates were dominated by an encrusted.

sponge mat (Spon-gillidae).

Dense growths of the filamentous green algae Cladophora sp. and Mougeotia sp. occurred where sponge growth was lacking.Pennate diatoms (Navicula spp., Nitzschia spp., Gomphonema spp.and Cymbella spp.), centric diatoms (Melosira spp.T, blue-green algae (Oscillatoria spp. and Anabena sp.), euglenophytes (Euglena sp., Phacus sp. and Trachelomonas spp.) and various green algae (Actinastrum sp., Chlamydomonas spp., Closterium sp., Pandorina sp. and Scenedesmus spp.) were among the flora associated with both sponge and algae mats. Invertebrates in the periphyton in-cluded crayfish, insects (Chaoborus sp. and Coleoptera larvae), Cladocera (Alona sp.), rotifers (Brachionus spp., Polyarthra sp.and Keratella spp.) and Nemata.2.2.3.5.2 Macrophyton Hamilton and Gin Lakes did not support a vascular aquatic plant assemblage of any significance during the preconstruction study period. None of the common vascular plants such as Potamogeton, Elodea, and Myriophyllum were observed.

It is possible that extreme annual fluctuiation in lake levels due to flooding pre-vented these rooted plants from becoming established.

The only aquatic plant recorded in the lakes was big duckweed, Spirodela spp. Portions of the northern end of Gin Lake contained a sparse population of this duckweed in the fall of 1972. These floating plants were flushed from the lakes by flooding in Novem-ber 1972. After floodwaters receded in July 1973, sparse popu-lations again established in both lakes. This cycle of flushing by floodwaters and repopulation following the floods is probably a normal event in the lakes.2.2.3.6 Disease and Pest Infestations in Fish Fish generally harbor a number of parasites and pathogenic or-ganisms to which they are mutually adapted. Although these in-festations cause stress to varying degrees, depending on condition of the host fish and environmental conditions, mortality due to natural causes (old age) is probably the largest single cause of death in an adult fish population (Ref. 54). Any outbreak of disease required the simultaneous occurrence of three factors: 2.2-76 GG ER'} (a) a susceptible host, (b) the pathogenic organism (e.g., virus, bacteria, parasite), and (c) a predisposing condition (e.g., low oxygen, food shortage, rapid temperature fluctuation, high popu-lation density).Review of pertinent literature and contacts with Dr. Glynn Hoffman (Ref. 55), Dr. Thomas Wellborn, Jr. (Ref. 56), and Mr. Barry Freeman (Ref. 57) indicated that no parasite or infectious disease outbreaks have been recorded in the Lower Mississippi River between 1973 and 1976.The likelihood of such outbreaks occurring is considered very small.since most recorded outbreaks in the Southeast have occurred in fish cultures (e.g., fish farming, fish hatcheries) (Ref. 56).Rogers (Ref. 58) reported that parasites were responsible for 30 percent of the fish kills investigated in the southeastern United States over a 5-year period. Bacteria were responsible for 35 percent of the fish kills during the same period. A parasitic protozoan, Ichthyophthirius, was responsible for a large shad kill in the Coosa River in Alabama (Ref. 59). Such outbreaks are unusual in a natural environment.

During preconstruction studies, incidents of infestation or para-sitism were recorded when noticed, either in the field or labora-tory. From April through August 1973, systematic observations were made during normal field sampling activities.

Leeches were the most commonly encountered ectoparasite; the majority of these leeches were attached to the fins. Approxi-mately 20 percent of the blue catfish specimens were infested;freshwater drum (9 percent) and channel catfish (4 percent) were also occasionally infested by the ectoparasite.

An infestation by a myxosporidean occurred on blue catfish in April 1973. This parasite's life cycle is direct from one fish to another. While resident in the flesh, the organism is encased in a large cyst, somewhat blister-like in appearance.

In April, 23 of 57 blue catfish examined (40 percent) were infested by this parasite.

The degree of infestation varied from a single cyst on a fish to almost complete coverage of the body on other fish.By June, the incidence of infestation had decreased to 9 percent when only 4 of 45 fish were observed with cysts. None of the blue catfish collected in August were infested.

This ectoparasite was not observed on any other fish species.Several other pests were noted during the study. A low inci-dence of occurrence of the parasitic copepod Lernea was observed on bluegill (2 percent), carp (1 percent), an blWue catfish (1 percent).

Many of the fish collected possessed low numbers of trematodes, Gyrodactylus and/or Dactylogyrus, on the gills;none, however, appeared seriously affected.

A few fish bearing the fungus Saprolegnia or Achlya on body lesions were also collected.

2.2-77 GG ER Two of these fish, both largemouth buffalo, had extensive body lesions of suspected bacterial origin; both fish appeared stressed by the infections.

Tapeworms were common in many of the fish collected.

The fish, however, did not appear stressed by the presence of these intestinal parasites.

Intestines of several shovelnose sturgeons contained roundworms.

With the exception of the two largemouth buffalo, afflicted fish appeared normal.The buffalo, however, were obviously stressed by the severe body infections they carried.A fish kill of moderate proportions (approximately 200 fish)occurred in Hamilton Lake on August 26 and 27, 1973. The fish were primarily shad, drum, and a few catfish. Although the cause of the kill was undetermined, dissolved oxygen depletion was suspected as the causative agent. Nocturnal dissolved oxygen depletion at the lake bottom was recorded in the summer and stress was probably added by very warm water temperatures (ca.30 C).2.2.3.7 Endangered or Threatened Fish Species There are no fish species which have been designated as endangered or threatened by the U.S. Fish and Wildlife Service (Ref. 7), the Mississippi Game and Fish Commission (Ref. 12) or the Mississippi Natural Heritage Program (Ref. 13) that are known to be resident in waters on or adjacent to the Grand Gulf site.One threatened species, the Bayou darter (Etheostoma rubrum), is endemic to the Bayou Pierre system which drains into the Missi-ssippi about 10 miles south of Grand Gulf.The Endangered Species Committee of the American Fisheries Society has published a 1971 assessment by states suggesting the status of threatened freshwater fishes in the United States (Ref. 43).Six species have been suggested as threatened in the Mississippi and concern is expressed for their survival.

The shovelnose sturgeon, listed as depleted, is the only one of these species expected to occur in the site vicinity (Ref. 42). Shovelnose sturgeon were common, however, in gill and trammel net catches at station 1 in the Mississippi River; 108 specimens were collected:

aproximately 20 of these were preserved for further study; the remainder were returned to the river. The shovelnose sturgeon population in the site vicinity appears to be abundant.Species listed as rare in Louisiana (Ref. 43), which has also been reported as possibly occurring in the Grand Gulf vicinity (Ref. 42), are listed below: Pallid sturgeon (Scaphirhynchus albus)Stoneroller (Campostoma anomalum)Bluntnose shiner (Notropis camurus)Suckermouth minnow (Phenacobius mirTbilis)

Steel color minnow (Notropis whipplei)Bluntnose minnow (Pimephales notatus)Rainbow darter (Etheostoma caeruleum) 2.2-78 GG ER Two pallid sturgeon specimens were collected from the Mississippi River at stations 1 and 9 and preserved for verification of the identifications.

Confirmation of the specimen identification was made by Dr. Reeve M. Bailey (Ref. 60). One of these specimens has been reposited in the Museum of Zoology, University of Michigan, Catalog No. UMMZ 194245. The pallid sturgeon is cur-rently classified as "status-undetermined" by the Bureau of Sport Fisheries and Wildlife.

A status-undetermined species is one that has been suggested as possibly threatened with extinction, but one about which insufficient information exists concerning its abundance and distribution.

Results of the.Grand Gulf field study indicate a very low abundance of pallid sturgeon in the Grand Gulf vicinity.The bluntnose minnow and stoneroller were both common in collections from site stream A in February 1972. Two bluntnose minnows were collected at Mississippi River station 1 in August 1973. A few larvae of the stoneroller were collected at station 3 in March 1973 and at station 6 in both March and April 1973.2.2-79 GG ER 2.2.4 References

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White-tailed Deer in the Southern Forest Habitat. Southern Forest Experiment Station, Nacogdoches, Texas, pp. 42-45.2. Yancey, R. K., 1970. "The Vanishing-Delta Hardwoods:

Their Wildlife Resources," La. Conservationists, March-April, p 26.3. Putnam, J. R., G. -M. Furnival and J. S. McKnight, 1960."Management.

and Inventory of Southern Hardwoods," Handbook No. 181, U. S. Department of Agriculture, Washington.

4. Murphy, P. K., 1973. Personal Communication.

Graduate Student, School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge.5. Noble, R. E., 1972. Personal Communication.

School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge.6. Robbins, C. S., B. Brunn, and H. S. Zim, 1966. "Birds of North America," Golden Press, New York.7. U. S. Department of the Interior.

1976. "Endangered and Threatened Wildlife and Plants." Federal Register, Vol. 41 (208): 47180-47198

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Chief, Game and Fisheries Division, Mississippi Game and Fish Commission, Jackson.12. Public Notice 1790, April 9, 1975. An order and regulations adopting an official list of endangered or threatened vertebrates in Mississippi, State Game and Fish Commission, Jackson.13. Mississippi Natural Heritage Program 1977. Special Plant and Animal Lists for the State of Mississippi.

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2.2-80 GG ER 15. Lack, D., 1954. "The Natural Regulations of Animal Numbers," Oxford University.Press, London.16. Golly, F. B., 1962. "Mammals of Georgia," University of Georgia Press, Athens.17. Hayden, D. C. and W. F. MacCallum, 1976. "Effects of prolonged flooding on small mammal populations in an area of thR Lower Mississippi River Valley," J. Miss. Academy of Sci., Vol. XXI: 84-88.18. Uhlig, H. G., 1956. "The Gray Squirrel in West Virginia." Bulletin 3, West Virginia Conservation Commission, Division of Game Management, Charleston.

19. Brandt, G. W., 1938. "A Study of Beaver Colonies in Michi-gan." Journal of Mammalogy 19: 139-162.20. Burt, W. H. and R. P. Grossenheider, 1964. "A field Guide to the Mammals," Houghton Mifflin Company, Boston.21. Glasgow, L. L. and R. E. Noble, 1971. "The Importance of Bottomland Hardwoods to Wildlife." Proceedings Symposium on Southeastern Hardwoods, U. S. Department Agricultural Forest Service, State and Private Forestry, Atlanta, Ga.: 30-43.22. Neal, W. A., 1973. Personal Communication, Game Biologist, Mississippi Game and Fish Commission, Jackson.23. Murphy, P. K., 1974. "The Monthly Availability and Use of Browse Plants by Deer on a Bottomland Hardwood Area in Tensas Parish, Louisiana." M. S. Thesis Submitted to Graduate School, Louisiana State University, Baton Rouge.24. Conant, R., 1958. "A Field Guide to Reptiles and Amphibians," Houghton Mifflin Company, Boston.25. Cook, F. A., 1942. "Alligator and Lizards of Mississippi," State Wildlife Museum, Jackson, Mississippi.

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Former Commercial Fisherman, Grand Gulf, Mississippi.

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412-422.48. Taber, C. A., 1969. "The Distribution and Identification of Larval Fishes in the Buncombe Creek Arm of Lake Texoma with Observations on Spawning Habits and Relative Abundance." Ph.D. Thesis, University of Oklahoma, Norman.49. Starrett, W. C., 1951. "Some Factors Affecting the Abun-dance of Minnows in the Des Moines River, Iowa." Ecology 32(1): 13-27.50. Breder, C. M. and D. E. Rosen, 1966. "Modes of Reproduction in Fishes," T. F. H. Publications, Jersey City, New Jersey.51. Daiber, F. C., 1953. "Notes on the Spawning Population of the Freshwater Drum (Aplodinotus grunniens, Rafinesque) in Western Lake Erie." American Midland Naturalist 50(1): 159-171.52. Waters, T. F., 1965. "Interpretation of Invertebrate Drift in Streams." Ecology 46: 327-334.2.2-83 GG ER 53. Hutchison, G. E., 1967. "A Treatise on Limnology," Vol. II."Introduction to Lake Biology and the Limnoplankton," John Wileys and Sons, New York.54. Ricker, W. E., 1954. "Causes of Death Among Indiana Fishes." Transactions of 10th American Wildlife Conference, American Wildlife Institute, Washington:

267-279.55. Hoffman, G., 1976. Personal Communication.

Parasitologist, U. S. Department of Interior, Fish Farming and Experimental Station, Stuttgart, Arkansas.56. Wellborn, T. L., Jr., 1976. Personal Communication.

Fish Parasitologist, Agricultural Extension Service, Mississippi State University, State College, Mississippi.

57. Freeman, B. 0., 1976. Personal Communication, Chief, Fisheries Division, Mississippi Game and Fish Commission, Jackson.58. Rogers, W. A., 1969. "A Summary of Fish Disease Cases Received Over a Five-Year Period at the Southeastern Cooperative Fish Disease Laboratory." Presented at 23rd Annual Conference, Southeastern Association of Game and Fish Commissioners, Mobile. (Mimeograph Copy).59. Allison, R. and H. D. Kelley, 1963. "An Epizootic of Ichthyophthirus multifilies in a River Fish Population." Progressive Fish Culturist 19(2): 58-63.60. Bailey, R. M. (Chairman), 1970. "A List of Common and Scientific Names of Fishes from the United States and Canada," 3rd Edition. American Fisheries Society, Special Publication No. 6.2.2.84 GG ER 3.9 TRANSMISSION FACILITIES The Grand Gulf Nuclear Station is linked to load demand areas by a system of transmission lines. Planning studies have shown that the most practical means of transmitting the approximately 2500 MW generated is to interconnect the station with existing 500 kV transmission facilities.

A map of the MP&L service area showing the existing transmission system is presented in Figure 3.9-1.The most economical transmission line routing results from a minimum length (straight line) between the station and the existing transmission facilities.

However, environmental, economic, and engineering considerations require that, whenever possible, the routes be established away from areas that are densely populated, historically unique, ecologically sensitive, and/or aesthetically pleasing.NRC General Design Criterion 17, Electric Power System, requires that the station switchyard be supplied with offsite ac power by means of physically independent circuits to minimize simultaneous failure of all offsite power sources.3.9.1 Transmission Line Routes The transmission routing from the Grand Gulf Nuclear Station is shown in Figure 3.9-2. A 43.6-mile single-circuit 500 kV transmission line connects to the Franklin EHV Switching Station, located southeast of the site, and a similar 22-mile line con-nects to the Baxter Wilson Steam Electric Station and its EHV Switchyard.

A 5.5-mile single-circuit 115 kV transmission line to the Port Gibson Substation provides construction power and an alternate source of emergency startup power. These trans-mission lines are required for operation of Unit 1. A third 500 kV transmission line, 24 miles in length, connects the Grand Gulf Nuclear Station to the Ray Braswell EHV Substation located northeast of the site and is required for operation of Unit 2.3.9.1.1 Baxter Wilson Steam Electric Station Route A 22-mile single-circuit 500 kV transmission line connects the Grand Gulf Nuclear Station to the Baxter Wilson EHV Substation near Vicksburg, Mississippi..

This connection utilizes the existing' EHV system emanating from the Baxter Wilson Steam Electric Station, thus connecting the Grand Gulf Nuclear Station with trans-mission lines serving northern Mississippi, northern Louisiana, and Arkansas.3.9.1.2 Ray Braswell EHV Substation Route A 24-mile single-circuit 500 kV transmission line connects the Grand Gulf Nuclear Station to an existing 500 kV transmission line feeding into the Ray Braswell EHV Substation near Jackson, Mississippi.

3.9-1 GG ER Through deactivation of a 6.11-mile segment of the existing 500 kV line, this connection enables the Grand Gulf Nuclear Station to feed into the service area of the Ray Braswell facility without requiring the construction of an additional EHV switching station or substation.

3.9.1.3 Franklin EHV Substation Route A 43.6-mile single-circuit 500 kV transmission line connects the Grand Gulf Nuclear Station to the Franklin EHV Substation.

The Franklin EHV Substation is centrally located to serve as a focal point of high-voltage distribution to a large area. This station is tied to the north by a 500 kV line from the Ray Braswell EHV Substation and to the south by a 500 kV line of the Gulf States Utilities System which serves southeastern Louisiana (see Figure 3.9-1). The line from the Grand Gulf Nuclear Station facilitates a three-way feed into the load center served by the Franklin Substation.

Juncture with the north-south EHV trunkline at any other point would require the construction of another EHV switching station and additional lower voltage transmission lines.3.9.1.4 Port Gibson Substation Route A 5.5-mile single-circuit 115 kV transmission line connects the Grand Gulf Nuclear Station to the Port Gibson Substation.

This connection provides construction power and an alternate source of emergency startup power.3.9.2 Route. Selection Reconnaissance surveys were conducted for each of the four proposed lines to establish flight patterns for aerial strip photography.

Several possible routes were outlined on state highway planning maps, and the most feasible general routing corridor for each line was selected.

Each corridor was then flown and photographed, a mosaic was compiled from the photo-graphs of each corridor, and alternate alignments for each route were studied. A ground reconnaissance team, consisting of two terrestrial biologists and a construction specialist, collected field data from representative areas throughout the length of each corridor.

These ground reconnaissance data were evaluated to determine the most desirable routing in each corridor.Factors considered in final route selection included: a. Historic sites b. Physical and aesthetic effects on the environment

c. Wildlife, particularly rare or endangered species, occurring along the routes d. Current private land use 3.9-2 GG ER e. Current and future public land use f. Restoration and multiple use of line right-of-way corridors q. Maximum utilization of proposed transmission design capabilities

h. Line construction and maintenance

i. Right-of-way acquisition The design of the transmission lines has been guided by the De-partment of Interior/Department of Agriculture publication entitled"Environmental Criteria for Electric Transmission Systems" and the Federal Power Commission publication, "Electric Power Trans-mission and the Environment." 3.9.3 Route Descriptions Current land use and basic plant communities along the transmis-sion line routes are summarized in Tables 3.9.1 and 3.9.2, res-pectively.

A summary of plants and wildlife typically occurring in various basic plant communities is presented in Table 3.9.3.Various physical characteristics (e.g., major highway and river crossings) along the routes are compared in Table 3.9.4. Details of specific features, especially potentially aesthetically sensi-tive areas along each transmission line route, are discussed below.The transmission line routings do not materially affect current land use. No residences were relocated along the routes.3.9.3.1 Baxter Wilson Route The 22-mile single-circuit 500 kV transmission line route to the Baxter Wilson Substation has been located as far east of the Grand Gulf Military Park as practical.

Approximately 110 trans-mission line towers are required to construct this line.The right-of-way traverses a rural, sparsely populated area with agriculture and forestry as the predominating land uses.With the exception of MP&L's property, this line traverses only one small industrial area (see Figure 3.9-3). This route passes through approximately 10.3 miles of hardwood forest, markedly irregular loessial bluff terrain, 1.7 miles of relatively flat hardwood-forested Big Black River bottomland, and 10 miles of farmland located on the Mississippi River floodplain.

The northern portion of the route runs parallel to .an existing 115 kV line for 6.9 miles. Approximately 3 miles of this section of the route is located 1/4 to 1/2 mile west of U. S. Highway 61 and the adjacent Illinois Central Gulf Railroad tracks.. This route also runs parallel to and approximately 100 feet east of an existing 13 kV distribution circuit right-of-way for 2.2 miles, in Warren County.3.9-3 GG ER Areas of potential aesthetic sensitivity occurring along this route are described below and are keyed to like numbers in Figure 3.9-3 which are indicated in parentheses following each heading.a. Grand Gulf Military Park Observation Tower (1)This 55-foot-high tower, located on the loessial bluffs overlooking the Mississippi River, provides a panoramic view of the Grand Gulf Military Park area. The tops of some transmission towers are partly visible from the observation tower as one looks eastward away from the Mississippi River. To minimize the adverse aesthetic impact, the powerline route has been located as far east of the tower as practicable (approximately 10,000 feet).b. Grand Gulf Boy Scout Trail (2)The powerline crosses a dirt road that is used as a hiking trail by Boy Scouts when they camp at the Grand Gulf Military Park. The crossing is in a wooded area where the aesthetic impact is minimal.C. Big Black River Crossing (3)The powerline crosses the Big Black River parallel and adjacent to the Illinois Central Gulf Railroad crossing.This crossing is in a remotely wooded area, and the aesthetic impact is negligible.

d. U. S. Highway 61 (4)For approximately 3.6 miles, the powerline parallels an existing 115 kV line located approximately 1/4 to 1/2 mile west of U. S. Highway 61. This entire area is cur-rently used as soybean fields and pastures; the powerline is, therefore, visible to motorists looking west from the highway. The Illinois Central Gulf Railroad tracks are located adjacent to the western shoulder of the highway at this point. The existence of the present transmission line and railroad facilities near to and visible from the highway minimizes the adverse aesthetic impact created by constructing the 500 kV transmission line in this area.The Baxter Wilson route does not cross any prime farmland (capa-bility Class I) within Claiborne County (Ref. 4). Within Warren County the route passes over about 35 acres of capability Class I soils (Ref. 5). Soil types crossed are Memphis silt loam (0-2 percent slope) (3.5 acres) and Commerce silt loam (31.5 acres).The former series consists of nearly level, deep, well-drained, and 3.9-4 Amend. 1 3/79 GG ER moderately well drained soils on the loessial uplands. This series is well suited for row crops, small grains, most grasses and legumes, and pecans. Commerce silt loam soils, located in alluvium along the Mississippi River, are nearly level and moderately well drained to somewhat poorly drained. This series is well suited to row crops, many grasses and legumes, and pecans. Memphis silt loam (0-2 percent slope) soils cover about 2790 acres, or 0.8 percent of Warren County, while Commerce silt loam covers 3135 acres, or 0.9 percent of the county. Including all Class I soils, there are 18,570 acres of prime farmland in Warren County.Thus, the acreage of prime farmland crossed is minimal when com-pared to the county as a whole.3.9.3.2 Ray Braswell Route A 24-mile single-circuit 500 kV transmission line, requiring the construction of approximately 125 transmission towers, connects the Grand Gulf Nuclear Station to the 500 kV Ray Braswell line southeast of Vicksburg.

Between the nuclear station and U. S. Highway 61, this route tra-verses approximately 11 miles of almost entirely unpopulated hardwood forest, markedly irregular loessial bluff terrain, and 3. 9-4a Amend. 1 3/79 I 1 GG ER 1.4 miles of relatively flat, hardwood-forested Big Black River bottomland (see Figure 3.9-3). North of U. S. Highway 61, the route passes through about 12 miles of sparsely populated loessial bluff hardwood or mixed hardwood and pine forest, interspersed with small farms and occasional residences.

This route crosses the Big Black River and U. S. Highway 61 and traverses an undeveloped portion of the Lake Park Estates resi-dential development southwest of Vicksburg.

Areas of potential aesthetic sensitivity occurring along this route are described below and are keyed to like numbers in Figure 3.9-3 which are indicated in parentheses following each heading.a. Grand Gulf Military Park Observation Tower (1)This 55-foot-high tower, located on the loessial bluffs overlooking the Mississippi River, provides a panoramic view of the Grand Gulf Military Park area. The tops of some transmission towers are partly visible from the observation tower as one looks eastward away from the Mississippi River. To minimize the adverse aesthetic impact, the powerline route has been located as far east of the tower as practicable (approximately 10,000 feet).b. Grand Gulf Boy Scout Trail (5)The powerline crosses a dirt road that is used as a hiking trail by Boy Scouts when they camp at the Grand Gulf Military Park. The crossing is in a wooded area where the aesthetic impact is minimal.c. Big Black River Crossing (6)The powerline crosses the Big Black River in a remote wooded area, creating a negligible impact.d. U. S. Highway 61 Crossing (7)The powerline crosses U. S. Highway 61 near an existing crossing of a 115 kV transmission line. The area is wooded and the crossing occurs at a curve in the high-way. Shielding by the curve and the trees minimizes the aesthetic impact of the powerline on motorists.

e. Lake Park Estates Residential Development (8)The powerline crosses the Lake Park Estates housing development about 2 miles southeast of Vicksburg.

The routing utilizes an undeveloped section of the develop-ment that is a mixture of pasture and small woodlots.3.9-5 GG ER Most of the houses in this development are built near a lake located about 1 mile east of the route. This routing does not require the relocation of any houses.This transmission line creates only a minimal adverse aesthetic impact.The Ray Braswell route does not cross any prime farmland within Claiborne County (Ref. 4); it does cross about 16 acres within Warren County (Ref. 5). Soils crossed include Memphis silt loam (0-2 percent slope) (14 acres) and Memphis and Loring silt loam (0-2 percent slope) (2 acres). Both soil types are in capability Class I-i and are nearly level, deep, well-drained, and moderately well drained. Soils in this capability class are found in the loessial bluffs and are well suited for row crops, small grains, most grasses and legumes, and pecans. Memphis silt loam (0-2 percent slope) soils cover about 2790 acres, or 0.8 percent of Warren County, while Memphis and Loring silt loam (0-2 percent slope) covers 320 acres, or 0.1 percent of the county. Including all Class I soils, there are 18,570 acres of prime farmland in Warren County. Thus, the acreage of prime farmland crossed is small when compared to the county-wide figures.3.9.3.3 Franklin Route A 43.6-mile single-circuit 500 kV transmission line, requiring the construction of 212 transmission line towers, connects the Grand Gulf Nuclear Station to the Franklin Substation southeast of the site. This route traverses approximately 10 miles of loessial bluff hardwood forest and fields, and 34 miles of pine and hard-wood forested gently rolling hills interspersed with small farms (see Figure 3.9-4).Major highways crossed by this route are U. S. Highway 61, the Natchez Trace Parkway, Mississippi Highway 28, and Mississippi.

Highway 550.: This route also crosses Bayou Pierre and the Homochitto River and traverses portions of the Homochitto National Forest..Other than U. S. Highway 61,'this route does not cross any heavily traveled roads or approach any populous areas. All road crossings are in rural areas and are nearly perpendicular.

Potentially ad-verse aesthetic impact on travelers is therefore minimal because of shielding by trees, particularly at the Natchez Trace crossing.The 6-mile segment immediately south of the station was selected to avoid the town of Port Gibson and the scene of the Civil War Battle of Port Gibson (see Figure 3.9-4). In addition, the Mosswood Country Club and golf course, located approximately 1 mile north of the U. S. Highway 61 crossing, is avoided by this alignment.

3.9-6 Amend. 1 3/79 GG ER Special consideration, was given to that portion of the line which necessarily crosses a part of the Homochitto National Forest. A possible route was considered that would pass through the National Forest boundaries entirely on privately owned land. However, this route would require paralleling the Homochitto River and was deter-mined to be aesthetically undesirable.

Through careful alignment adjustments, the route obtains a near perpendicular crossing of the Homochitto River. It passes through the forest boundaries on approximately

9.5 miles

of privately owned land and traverses only 1.6 miles of National Forest land. Multiple-use projects on the private land right-of-way corridors, similar to past practices by MP&L have been implemented.

See subsection 3.9.4.8 for a description of these projects.Areas of potential aesthetic sensitivity occurring along this route are described below and are keyed to like numbers in Figure 3.9-4 which are indicated in parentheses following each heading.3. 9-6a Amend. 1 3/79 1 1 GG ER a. Port Gibson Lookout (9)The Port Gibson Lookout is located on loessial bluffs overlooking the eastern bank of Bayou Pierre. To avoid the area of the Battle of Port Gibson, the powerline crosses Bayou Pierre within partial view of the look-out. The route is located in a thickly wooded area about 1 mile west of the lookout. A 100-foot buffer strip parallel with and on each side of the top bank has been selectively cleared to minimize the adverse aesthetic impact.b. Natchez Trace Parkway Crossing (10)The powerline crosses the Natchez Trace close to a thickly wooded area. A 50-foot buffer strip has been maintained to shield the transmission line from the view of motor-ists on the Trace.c. U. S. Highway 61 Crossing (11)The powerline crosses U. S. Highway 61 in a rural area south of Port Gibson. This crossing is in an open agricultural area and avoids the Mosswood Country Club.Trees shield the powerline from the vision of motorists driving south toward Natchez. The powerline is visible to motorists driving north for a distance of about 0.5 mile. The aesthetic impact of this crossing is there-fore minimal.d. Mississippi Highway 28 Crossing (12)The powerline crosses Highway 28 in a rural, semi-wooded pasture area. These conditions are typical along the highway, and the adverse aesthetic impact is minimal.e. Mississippi Highway 550 Crossing (13)The powerline crosses Highway 550 in a rural semi-wooded pasture area. As in the case of the Highway 28 crossing, these conditions are typical along the highway and the adverse aesthetic impact is minimal.f. Homochitto River Crossing (14)The powerline crosses the Homochitto River about 1500 feet south of the Mississippi Highway 550 bridge in a thickly forested area. Only the tower tops are visible to motorists.

The alignment of the right-of-way does not parallel the river, thereby minimizing the aesthetic impact on canoeists.

3.9-7 GG ER g. Homochitto National Forest Crossing (15)The powerline crosses the Homochitto National Forest almost entirely on privately owned land. About 1.6 miles of the line are located on National Forest land. This crossing occurs in a thickly wooded area and does not create any adverse aesthetic impact. An alternate route through the forest, entirely utilizing privately owned land, was rejected because it required paralleling the Homochitto River, which would create an adverse aesthetic impact.It is not possible to determine the acreage of prime farmland (capability Class I) crossed by the Franklin route in Jefferson and Franklin counties, since soil survey maps are not available for these counties.

Within Claiborne County the route crosses approximately

2.5 acres

of prime farmland.

All of it is classified as Memphis silt loam (0-2 percent slope) (Ref. 4). The characteris-tics of this soil type are discussed in Section 3.9.3.1. There are 6045 acres of Memphis silt loam (0-2 percent slope) and a total of 8200 acres of all Class I soils in Claiborne County.Thus, the line will affect only a small percentage of prime farmland in the county. There is no prime farmland in Lincoln County (Ref. 6).3.9.3.4 Port Gibson Route A 5.5-mile single-circuit 115 kV transmission line, requiring the construction of approximately 56 transmission line structures, connects the Grand Gulf Nuclear Station to the Port Gibson Substation.

This route traverses lightly populated agricultural areas of field and small woodlots (see Figure 3.9-4). The route alignment was adjusted to avoid residential areas of Port Gibson.A railroad spur was built from the Illinois Central Gulf Railroad tracks to the nuclear station. The 115 kV transmission line was constructed adjacent to this spur for approximately 2.4 miles, eliminating the ecological damage resulting from the clearing of an additional right-of-way corridor for the transmission line for this distance.The only area of potentially aesthetic sensitivity on this route is the U. S. Highway 61 Crossing, which is shown in Figure 3.9-4 as Location 16. The crossing is located in a nonscenic commercial area containing two gasoline stations and oil storage tanks. The aesthetic impact of the powerline is therefore negligible.

The Port Gibson route crosses about 3.8 acres of prime farmland within Claiborne County (Ref. 4). All of this is classified as Memphis silt loam (0-2 percent slope), the characteristics of which are discussed above (see section 3.9.3.1).

This repre-sents only a small portion of the total acreage of Class I soils within the county (8200 acres).3.9-8 Amend. 1 3/79 GG ER 3.9.4 General Features of Transmission Line Corridors Many features requiring consideration during transmission line route selection are common or at least similar for all of the transmission line routes emanating from Grand Gulf Nuclear Station.These general features are described in this subsection.

Specific descriptions of each transmission line route are presented in subsection 3.9.3.3.9.4.1 Current Land Use Approximately 98 percent of the land adjacent to all of the transmission line corridors is currently used for forestry (58 per-cent) or agricultural (40 percent) purposes.

The remaining land is presently used for residential (1 percent) or industrial (1 per-cent) purposes.

Current land use types are quantified in miles 3. 9-8a Amend. 1 3/79 GG ER for each transmission line route in Table 3.9.1 and are illus-trated for the Baxter Wilson and Ray Braswell routes in Figure 3.9-3 and for the Franklin and Port Gibson routes in Figure 3.9-4.Almost all of the land may be utilized for recreational hunting.3.9.4.2 Aesthetic Considerations The clearance of right-of-way corridors in wooded areas and the intrusion of man-made structures may have an adverse impact on the scenic beauty of an area. Aesthetic values are difficult to evaluate inasmuch as they vary with the individal observer.To minimize the adverse aesthetic impact of the Grand Gulf trans-mission line corridors, areas of potentially aesthetic sensitivity were identified and evaluated in designing the routes. Emphasis was placed on minimizing adverse aesthetic impact in areas of particular natural beauty, in residential areas, and at all major highway and river crossings.

3.9.4.3 Historical Sites The Grand Gulf Nuclear Station site is located in an old and historic section of Mississippi.

Claiborne County was one of the first counties organized in the State and contains many historic features, including antebellum homes, Civil War battlefields, and Indian relics. The northern boundary of the site is adjacent to the Grand Gulf Military Park, which is included in the National Register of Historic Places.To determine the location of historically significant sites in the vicinity of the station and the transmission line corridors, MP&L has conducted historic site analyses which included the funding of a survey by the Mississippi Department of Archives and History.Information obtained from this survey was used to ensure that the transmission line routes avoid historically important areas.3.9.4.4 Dominant Plants and Animals The basic plant communities occurring along the transmission line routes and the estimated length and acreage of right-of-way in each basic plant community are presented in Table 3.9.2. The lo-cations of these basic plant communities along transmission line routes are shown in Figures 3.9-3 and 3.9-4. The common plant and animal species typically occurring in each basic plant community are listed in Table 3.9.3.Forests in the western portion of Mississippi are typically domi-nated by oak, hickory, and sweetgum in loessial bluffs; oak, sugar-berry, and green ash in river bottomlands; and loblolly pine and shortleaf pine in upland hills. In most instances, the same forest-dependent wildlife species are commonly found in all three forest communities.

3.9-9 GG ER 3.9.4.5 Rare or Endangered Species With the exception of the red-cockaded woodpecker (Dendrocops borealis), no rare or endangered species are known to be resident in the vicinity of the transmission line routes. The last reported records of rare or endangered species resident in southwest Mississippi are those of red wolves in 1946 and bald eagles prior to 1960. Four sightings of black bear have occurred on the Grand Gulf Nuclear Station site in 1977 (see subsection 2.2.2.7).The red-cockaded woodpecker, a resident of pine forests, is known to be nesting in portions of the Homochitto National Forest.After the right-of-way of the Franklin line was surveyed and staked by engineers, surveys were conducted to determine if any red-cockaded woodpecker nesting colonies lie within the right-of-way boundaries.

No such colonies were found.Rare or endangered terrestrial species, which formerly occurred in southwest Mississippi, are listed below: Red wolf (Canis niger)Puma (Fe--s concolor)Southern bald eagle (Ha-1-aetus

.leucocephalus)

Peregrine falcon (Falco egrinus)Osprey aliaetus)Eskimo curlew (Neumenius borealis)Bachman's warbler (Vermivora bachmanii)

The red wolf and puma are wilderness species which were extirpated from the region as the result of hunting and destruction of habitat.Suitable habitat for these species is present in the areas traversed by the transmission line routes. A summary of records of Mississippi land mammals compiled by Wolfe (Ref. 1), however, indicates that the last authenticated record of any of these species occurring in this region was in 1946 when a red wolf was collected in Claiborne County.The bald eagle, osprey, peregrine falcon, and eskimo curlew may occur in this region, particularly along the Mississippi River, during migration.

The bald eagle was reported nesting in the Mississippi River bottomland region north of the Big Black River prior to 1960 (Turcotte, personal communication, 1972). The transmission line routes are located east of the Mississippi River bottomlands and should not infringe on this potential eagle nesting habitat.Bachman's warbler is a very rare species that inhabits moist decid-uous woodlands.

Records in the Mississippi Museum of Natural Science indicate the species is not present in the vicinity of the transmission line routes.3.9.4.6 Soils A soil-type map showing the areas of Mississippi that are traversed by the transmission line corridors is shown in Figure 3.9-5. The 3.9-10 GG ER corridors cross three basic categories of soil types: Mississippi Delta, brown loam, and thin loess. The following descriptions of these types were obtained from Reference 2.a. Mississippi Delta In the Delta area, the alluvial soil materials were deposited by the Mississippi River and other tributary streams.Since these materials were washed in from a broad and variable region covering the northern and western states, they vary in nature and composition.

The fertility level is high, and young soils of the Delta are greatly influenced by the soil materials from which they developed.

Generally, the land in the Mississippi Delta is almost level, which is characteristic of most large floodplains.

The lay of the land ranges from large flat areas of"buckshot" or slack-water clays to gently sloping natural levees.b. Brown Loam (Thick Loess)The soils of the brown loam area developed from loess or windblown material which is generally over 4 feet thick. This is the most uniform soil material found in Mississippi.

Because of this uniformity in parent material, the number of different soils is small in comparison with other land resource areas. They are all high in silt content and, when sloping and steep, are subject to severe erosion. The uniform parent material contains sufficient native fertility for rapid plant growth. This is reflected in the production of forage and other crops throughout the brown loam area.The lay of the land varies from level to steep and rugged. Soil erosion is common on the sloping and steep land where protective cover is not provided.On the other hand, the soils respond well to good management and are suitable for many uses.c. Thin Loess The soils in the thin loess area (less than 4-feet thick) are composed of silty material and overlie the various kinds of coastal plain materials.

Under these conditions, the underlying materials influence soil development greatly and affect the erosion hazards of the area.Gully erosion has been observed in the fields where the soils have loamy sands and sand under them. Such conditions have made it necessary to employ erosion control and flood-prevention measures.3.9-11 GG ER The soils of this area are highly weathered and have reached the point where the fertility level is low.Complete fertilizers are needed for the production of all nonlegume crops, and lime is needed for most legumes.3.9.4.7 Alternate Routes and Alignments Selection of the transmission line routes was based partially on maximum utilization of existing electrical transmission facilities.

Preliminary plans were to construct transmission lines connecting the Grand Gulf Nuclear Station to the Franklin EHV Substation, the Baxter Wilson EHV Substation, the Port Gibson Substation, and an EHV Substation in Sterlington, Louisiana.

As a result of route surveys, the Sterlington route was replaced by the Ray Braswell route because the powerlines of the original route would have crossed the Mississippi River and traversed eco-logically sensitive Mississippi River bottomland hardwood forest, thus creating an adverse aesthetic and environmental impact. Addi-tionally, the projected cost of the 79-mile line for the Sterlington route was significantly more than for the 24-mile Ray Braswell route.The alignment of the original Baxter Wilson route was adjusted to avoid traversing approximately 6 miles of ecologically sensitive, mature, Mississippi River bottomland hardwood forest. This eco-logically sensitive bottomland area has been avoided by shifting the alignment eastward to an abandoned 13 kV right-of-way that runs through loessial bluffs adjacent to the bottomlands.

The Franklin Route is not the most direct tie-in with the north-south EHV trunk line. The most direct tie-in with that trunk line would be a line going due east from the station, approximately 30 miles. However, since there currently is no switching station in this area, one would have to be constructed.

In addition, new, low voltage transmission lines from this switching station would be required.

The environmental and economic savings by using this more direct routing would be more than offset by the addition of a new switching station and the required new low voltage transmission lines.There were no viable alternative routes considered for the Port Gibson line inasmuch as aesthetically pleasing, ecologically sensitive, historically important, and densely populated areas could be almost entirely avoided by minor route adjustments.

3.9.4.8 Multiple-Use Projects A multiple-use wildlife project was formulated on a portion of the Ray Braswell Gulf States Utilities 500 kV line which passes through Copiah County, Mississippi.

Working with the property owner, MP&L, 3.9-12 GG ER guided by recommendations of the U. S. Soil Conversation Service, reconditioned and seeded the cleared right-of-way.

The utility corridor serves as a functional fire lane and affords both cover and forage for wildlife.

The project has received enthusiastic support from conservationists, sportsmen, and the general public in the area. Another multiple-use project was initiated by MP&L to restore some 200 miles of EHV transmission corridors.

Utilizing specifications and guidelines adopted by the Soil Conservation Service, the cleared rights-of-way were reconditioned and reseeded for multiple-use purposes.

As a result of this extensive conser-vation project, MP&L received the first industrial award by the Mississippi Chapter of the Soil Conservation Society of America in 1968. In part, the citation read: "For outstanding accomplishments in soils and water conservation on 224 miles of EHV transmission line, covering some 1,100 acres from Attala County south to the Louisiana line and west from Jackson to Vicksburg." The presentation of the award and citation and the conservation work are cited in Reference 3.Similar multiple-use projects are being carried out on the trans-mission lines associated with Grand Gulf Nuclear Station. In addition to the construction procedures discussed in Section 4.2, MP&L is utilizing such techniques as selective cleaning, screening and handcutting in certain areas to minimize environmental impacts.Numerous food plots for wildlife have been planted in cooperation with surrounding landowners.

3.9.5 Description

of Transmission Facilities A typical nonguyed galvanized steel tower used by MPCL for 500 kV transmission lines is illustrated in Figure 3.9-6. The 115 kV transmission line is H-frame woodpole construction for 3.1 miles and single woodpole construction for 2.4 miles. Typical 115 kV transmission line towers of woodpole construction are illustrated in Figures 3.9-7 and 3.9-8 for H-frame and-single pole, respectively.

Right-of-way widths are 200 feet for the 500 kV lines and 100 feet for the 115 kV line. Typically, there are approximately 4.75 tower structures erected per mile for the 500 kV line, and approximately

8.5 tower

structures per mile for the 115 kV line. Long spans are used to reduce the number of structure sites. Ruling span for the 500 kV transmission lines is 1150 feet and the ruling span for 115 kV line is 600 feet for the H-frame portion and 500 feet for the single pole portion.3.9-13