Text

Interim Monitoring,1974-75
	ML20042B475
Person / Time
Site:	River Bend
Issue date:	04/15/1976
From:	Bryan C, Conner J; LOUISIANA STATE UNIV., BATON ROUGE, LA
To:	;
Shared Package
ML20041E806	List: ML20042B475; ML20042B477; ML20042B478; ML20042B482; ML20042B483; ML20042B486; ML20049J319; RBG-12241, Forwards Suppl 2 to Environ Rept Responding to NRC 820104 Questions & Including Corrections & Updated Info;
References
	RBC-3188, NUDOCS 8203250348
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{{#Wiki_filter:. kO-kb 4 (z \\o\\ \\ u t RIVER BEND STATION I!frERIM ECOLOGICAL MONITORING, 1974-75 by John V. Conner, Principal, Investigator C. Fred Bryan, Former Project Leader m k_,) Biennial Report Research Contract Between i Culf States Utilities Company d anil ~ Louisiana State University and A. and M. College l School of Forestry and Wildlife Management Baton Rouge, Louisiana i 1 April 15, 1976 ....[$i7'y. 0 e% p l ~ C0%f 8203250348 Y20310 PDR ADOCK 05000458 C PDR

O ACKNOWLEDGEMENTS The following persons did significant amounts of field and laboratory work in connection with this study: Barbara W. Bryan (water-4 chemistry and phytoplankton); Dugan S. Sabins (fishes); Timothy P. O'Brien (fishes); David J. DeMont (benthos); Larry Hartzcg (water chemistry); and Phillip Downey (benthos). Gary Saul and John Goyert, graduate assistants in the Department of Experimental Statistics, helped with data processing. 1 J eme AO l-i;_ l l i._ e l l. i I W I i F l s O 11 S s I f l

O TABLE OF C0!f!EITIS Page 4 1 INTRODUCTION..............

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METll0DS 10 WATER QUALITY. 10 l Mississippi River. i 12 { Alligator Bayou..... i 12 Grants Bayou.. 21 PHYTOPLANKTON...... Missis sippi River................... 21 ...........22 Alligator Bayou.... MACROZODPLANKTON AND DRIFT. 31 Qualitative composition. 31 Seasonal Patterns and Relative Abundance. 34 24-hour Study and Horizontal Distribution....... 37 i Ichthyoplankton.................... 41 56 BENTH0S.... Mississippi River......... ~.......... 56 Alligator Baycu.................... 57 58 Grants Bayou. 77 rISHES.. I l Mississippi River.. 77 i -. I 78 Alligator Bayou. 79 f -- Grants Bayou.. l 93 AMPHIBIANS AND REPTILES.................. LITERATURE CITED. ...........96 lii ( --

1 /" (j INTRODUCTION This report covers the first seven quarters of interim ecological monitoring at River Bend conducted by fisheries personnel of the LSU School of Forestry and Wildlife Management. Results of snap-trapping surveys of small mnmmals will be reported separately by Dr. L. L. Glasgow, under whose supervision the work was done. ~~ Most of the underlying report consists of tabulations and sumnaries of data, with discussions and interpretations limited chiefly to areas in which changes were apparent in comparison with baseline d ca presented in earlier documents. Since, however, meter-net sampling of macrozoo-plankton (including fish larvae and eggs) and drif t in the river received scant attention during the baseline survey, a more detailed discussion of the subject is presented. Similarly, a revised list of the herpeto-fauna of the site and its immediate environs 's presented, based on actual i observations made during 1974-75 at River Bend. Earlier information ~ presented on amphibians and reptiles was based primarily on literature and the experience of Dr. Glasgow in the Florida Parishes in general. All data recorded during this interim monitoring program are not included below, since they were deemed of little immediate concern. For ~ example, all tests for free residual chlorine in river water were negative, as expected in view of the absence of an nearby potential source. Bathy-metry traces made during each quarter at river transects reveal only minor changes in channel morphology. Observations made in West Creek revealed no changes from conditions reported earlier until site preparation activities began in autumn, 1975. Characterization of another intermittent upland tributary (that.on which ~

i i 2 I I l! impoundment for the " Wildlife Management Lake" is proposed) was accomplithed. It was found that, abo.a the lake site, flows occur only during and immediately after rains. At other times aquatic habitats consist of a l I few small, stagnant, rain pools supporting a limited irsect fauna and only tadpo:es among vertebrates. Changes have been noted in these upland '~ tributaries as a result of site preparation activities but these were manifested mainly after the period covered in this report and thus will be discussed later. Figure 1 is a map of the study area showing locations of routine l sampling activities. Figure 2 is a graph of river stages and discharge, i i compiled from data supplied by the U.S. Army Corps of Engineers, showing I sampling times and periods. i N i l f i i i i s _E f~ WW

~% 3- '\\.~'s e g I y% lQ N,~.,)k g ( -D ;)! S,1 ~ s [ t s S l I 3* J T 1 ig \\ y. I f 4 ~ O. j, Wi t e ./ f! l\\;'V'N i6" 'O 'I M,N ? m s# -n. Q< 49 ~ li [ s D g g 6*. L.. _.., 9 [". sf lun m u, D4 m. s fxrm s -f i' A3 (s, Figure 1. Mississippi River and tributaries on and near River Ber.d study (J area. Circles mark stations for routine quarterly sampling of water quality..phytoplankton, and benthos. Roman numbers mark river transects; Arabic numbers mark Alligator and Grants Bayou stations. Letters indicate where fish and tnacrozooplankton are sampled when hydrographic conditione permit (see text and Table 1; M = meter net, S = seine T = trammel net, H = hoopnet).

4 WWW 1 j 1974 n g' j = i I x s m \\ y 40- -e g l -7 w 1 I J,. 4 1 8 -5 i 3o. 1.,i. j -4 5 w 4 12, w. , w... u 1 [975 ~" O -n Ilf e I 1 f ~ l4 so- -e j l -s e dg...... .I h 8 m. ....,. 1............... g .s h4 f I 1 I g,, [1 22 1 73 k-h. h~'y -2 1.b A i I!', ', I JAN FEB MAR APR MAY JLEE JULY AUG SEPT OCT NOV-DEC ~ f Figure 2. Stage (Bayou Sara gage) ind discharge (Tarbert Landing) of Mississippi River, 1974-/5. Shaded areas indicate quarterly sampling periods. Arroni indicate macrozooplankton-sampling (meter-net) visits. Dasned line indicates stage above which flood plain inundation occurred; dotted line shows stage above which overbank flooding obtained. O1 _.v l i e.w l l

5 <~w t x_/ METHODS i Procedures and equipment used in this study are the same as those described in earlier reports with the exception of changes or additions ~ described below. Principal difference between the intensive baseline survey phase of 1972-73 and the current interim monitoring program involves the shift, for most sampling, from a monthly to a quarterly (seasonal) frequency of visits. A Hydrolab Surveyor Model 6D (Hydrolab Corp., Austin, Texas) was used for about half of the 131 situ water quality readings. This instru-ment is comparable in performance to the Martek instrument used for the remainder of the sampling (and all of the baseline survey work), except ~(' ) that it has the added advantages of a temperature-compensated conductivity x_. probe and slightly more compact and rugged construction. Free residual chlorine determinations are made immediately in the boat on surface samples from regular river transect stations using a f Hellige Standard Comparator (Hellige, Inc., Garden City, N.Y.) and the appropriate color disc (No. 333-D26). In conjunction with meter-net tows surface current velocities are i measured in cm/sec from the stationary vessel with a digital flowmeter I and deck readout (General Oceanics, Inc., Miami, Fla., Models 2030 and g ~ i 2035). The same instrument is used occasionally during tows to monitor boat speedc. Table 1 is a summary of sampling effort during the interim monitoring r^, phase covered in this report (spring 1974 through fall 1975). 's ) ~- Sampling for aufwuchs-type macroinvertebrates, as prescribed in Exhibit A of the current GSU-LSU contract, was not initiated on a routine

6 i i basis during the period covered in this report, because of inability to recruit a qualified graduate student until September 1975. Development of procedures and preliminary sampling were accomplished during autumn and winter, 1975-76, however, and routine sampling of the coccunities of Crassy Lake is being initiated as of this writing. Since the emergent cutgrass beds of Grassy Lake are apparently the richest and most unique of the aufwuchs communities on the study area, we consider them to be of highest priority. It is now clear that sampling'of submerged free substrates ~ will require special procedures and equipment in each separate macrohabitat i (river, Grassy Lake, lotic portions of Alligator Bayou) and will nowhere l be simple. Procedures for sampling aufwuchs in the river and Alligator Bayou Station 4 are being developed. l h For the cutgrass beds of Grassy Lake we have developed a double-cylinder device, similar in basic principle to that used by Wilding (1940). The outer cylinder is lowered over a clump of emergent grass and driven a i 1 few centimeters into the substrate to isolate the vegetation and surrounding i I' water column. The enclosed clump of' vegetation is then extracted by means of specially-designed hooks and retained for inspection of its surfaces. The water and surf ace layer of substrate inside the cylinder is then stirred up and a snugly-fitting inner cylinder with hinged bottom is inserted to isolate the suspension of animals and fine sediments. The I ~ second cylinder is fitted with screened portals (mesh equivalent to #30 sieve used in benthos sampling) and, when withdrawn, retains the animals that either dropped off the vegetation or were free-living in close f ') association with the plants. Due to the size and coarseness of the cutgrass, a as well as the water depths, it has been necessary to construct a special t I

7 j s (_ ) floating platform from which to operate the apparatus and pulley-driven levered hooks for up-rooting the plants, i Macroinvertebrates associated with woody substrates are being I sampled with small logs, cut to known dimensions, tethered for standardized intervals in various microhabitats. Prior to retrieval each log is entirely enclosed by a fine-mesh bag to retain any animals that might drop off due to disturbance and removal from the water. Although as yet used only in Grassy Lake, it la anticipated that these log samplers will be applicable in the lotic portions of Alligator Bayou and along the river margins. For the last habitat, indeed, the log samplers may prove to be the only practical means of studying aufwuchs-t,pc invertebrates. Population studies of larger fishes in Grassy Lake have also been ~( ) started. A boat-mounted, 220-volt A.C. boom shocker and 1-1/2 inch stretched mesh trap nets are being used to collect specimens. The electro-fishing equipment was used twice during this reporting period, and results are included below (see Fishes Section). Basic objective of this activity ( is to obtain population estimates of 'at'least some of the more common and important species (e.g. largemouth bass, crappies) during low-water periods when the lake is essentially isolated. Estimates will be made by mark-and-recapture exercises. Since fishes are being individually tagged it will also be possible, assuming adequate recaptures after sufficient periods I ~ at liberty, to glean information on growth and movements of certain fishes. Several hundreds of specimens have already been tagged and released. Two recaptures have been reported by local sport fishermen, although both r~~ were of fishes tagged and released in the river during a shakedown trip _L.) for equipment and procedures. A blue catfish was caught after two weeks

i 8 I at liberty, approximately three miles downstream from its point of release. r A largemouth bass (one of only two tagged!) was caught af ter six weeks at liberty, roughly eight miles downstream from its point of release. l t ennus i I t l i ~ f, I ~ l l f \\ l t ~ l l O W

( l-1 ( l i I I I i I ( l l I I I i ] Tcble 1. Su==ary of campling effert in equstic phnca cf interim cc31ogic21 conitoring program on the Rivar Bend study area, 1974-75. Annlyses/ Gear Frequencies / Locations /C'.4 cions / Levels Water Quality -in situ readings of te=perature, -quarterly from surface, mid-depth, and bottom at three stations conductivity, dissolved oxygen, pH across river Transects V, IV, and III; monthly or se=imonthly in (Martek/Hydrolab) conjunction with meter-netting (see below for stations); quarterly from surface at all Alligator and Grants Bayou stations. -lab or field analyses of bicar- -quarterly from surface at three stations across river Transects V, bonate alkalinity, total orthophos-IV, and III; quarterly from surface at all Alligator and Grants phates, nitrate nitrogen, turbidity, Bayou stations (chlorine not included outside river; turbidity free residual chlorine (Titration / analyses begun af ter Su=mer 1974. Spectrophotometry) Phytoplankton -two liter grab samples -quarterly from surface at three stations across river Transects V, IV, and III; quarterly from surface at three Alligator Bayou stations; quarterly from two Grants Bayou stations after Summer 1974. Macrozooplankton -two minute tows -monthly or semiconthly, depending on season, from three stations (0.505 cm mesh meter-net) across river Transect V,1974; monthly or semimonthly at river sta-tions V-A, IV-A, and III-A, 1975; monthly or semimonthly in lower Bayou Sara, March through early August, 1975; all tows at surface. Benthos -triplicate Petersen grabs -quarterly from bottom at three stations across river Transects V, l I IV, and III. -triplicate Ekman grabs -quarterly from bottom at three Alligator Bayou stations; quarterly from bottom at two Grants Bayou stations after Spring 1974. Fishes -trammel nets -quarterly at river stations V-A, V-E, III-A, and III-E (V-A } omitted at flood stages). -hoopnets -quarterly at river stations V-A, V-E, III-A, and III-E. -seines -quarterly at some or all stations marked "s" on Figure 1, depending upon hydrographic conditions. Bnthymetry -Raytheon fathometer -quarterly traces across river transects V, IV, and III. l e

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10 I'v') WATER QUALITY Mississippi River Seasonal summaries of several physicochemical characteristics of lower River samples from January 1974 through December 1975 are presented in Table 2. Data collected from all depths at all Stations of Transects III, IV, and V are combined; analyses for total orthophosphates, nitrate nitrogen, turbidity and bicarbonate alkalinity were made only on surface water samples. Generally, observations of physicochemical characteristics during ~ seasonal sampling trips 1974 - 1975 were similar to data averaged over comparable periods in 1972 - 1973 when sampling took place at twice-monthly intervals. However, there were notable exceptions. 1. Water temperatures were considerably warmer during early and -~ 1 ate 1974 and during the Summer and Fall 1975. 2. Conductivities and therefore presumably dissolved solids, were unusually high throughout most of 1975. 3. Dissolved oxygen approached saturation in the Summer 1974 (92%) and 1975 (99%); whereas during summertime the previous l two years, dissolved oxygen aversged only 77% of saturation. l 4. Turbidities were unusually low during most of the reporting period, and l 5. Bicarbonate alkalinity and pH were high during Summer and Fall 1974, and especially high during the summer sampling period in 1975. J.' # All these phenomena may be explained, at Icast partially, by the i high discharge and mild temperatures experienced during early 1974, by I

11 r the relatively low discharge throughout 1975 and by warm water temperatures during Summer and Fall 1975. Although negative correlations between dissolved oxygen and tempera-ture are expected in heterotrophic systems, dissolved oxygen in the river increased from Spring to Snmmer during 1974 and 1975 despite ten-perature increases. Apparently, this is an expression of increased primary production within portions of the reach during periods of low discharge. Estimates of total phytoplankton standing stocks were considerably higher ~~ during the Summer 1974 and 1975. Moreover, a diel study on August 27 - 28, 1974 demonstrated that there can be a net gain in dissolved oxygen in the lower River.especially in west-shore waters of Transect 5 (Table 3). Production / Respiration ratios, calculated using a modification of Lind's '() (1974; p. 118-119) technique, were +0.61 on the west-shore compared with -0.85 for midstream and -0.15 for east-shore waters. (Communities with P/R ratios commonly in excess of +1.0 are regarded as autotrophic.) Ours i were conservative estimates of gross primary production, since surface, f mid-depth and bottom readings were ' ncluded in the computation.- In i addition, a late af ternoon rain and windstorm stirred surface waters on the second day of the study and probably caused a loss of DO from waters { which had been supersaturated with oxygen before the storm. As in past reports, horizontal variations (Tables 4 and 5) in water i ~ quality are dwarfed by vertical (Table 6) and especially temporal (Table 2) variations in this reach. While it appears that horizontal differences were very small, west-shore waters were slightly warmer, less conductive, and more alkaline. Fewer observations were made at Transect IV and at -{"') mid-depths during winter months which may explain the elevated average WU w

12 ) temperatures tabulated for these waters (Tables 5 and 6).

Alligator Bayou Seasonal variations in water quality of Alligator Bayou are presented in Table 7.

Because station 2 is dry much'of the time and is similar in water quality to station 1 when there is flow in Alligator Bayou, this station was not sampled after March, 1974. Station 1 waters were influenced by high river stages from mid-November 1974 till early July 1975. During Spring sampling 1975 the entire floodplain was inundated and at least three of the four Alligator Bayou stations were affected by river waters at this time. As in the past years of study, upstream stations were generally cooler during the summer because of the canopy and warmer during the winter when lower stations were influenced by the river. Conductivities and alkalinities generally decreased upstream and dissolved oxygen was -- sU usually lowest in the lake station. Nutrients were usually highest in this system during periods of river water influence; however, a notable exception occurred in Summer 1974 at Station 4 when high total phosphate values may l have resulted from an accumulation of organic materials. Grants Bayou 'j Seasonal variation in water quality in Grants Bayou is presented in Table 8. The stream had been intermittent for several weeks prior to the t visit in the Summer 1974, and only JLt1 situ data were taken $n pools near [ the regular sampling station. During the Fall 1974, Station 1 was greatly I influenced by pumped discharge from West Creek. j i The stream remained slightly acid after the Winter 1975 sampling; It was low in conductivity, temperatures were generally cooler and dissolved [ oxygen higher at the downstream station, regardless of ecason (Tabic 8). i; Turbidities were usually highese when sampling took place during or I. b ,s; l'

13 immediately following a spate. The high total phosphates witnessed during the spring and summer sampling cannot be explained. es.s w e e end e d 9 es.S f 9.u. 41.F I tuuS e W 4

l' Table 2. Seasonal variation in selected physiccchemical charactetistics I of lower Mississippi River water near St. Francisv111e, Louisiar_a from January, 1974 through December, 1975. Units are mg/l unless indicated otherwise; means i standard deviation and range are presented. l 1974 1975 l January - April - July - October - January - April - July - Octob< l Characteristic n March n June n September n December n March n June n September n Dec ce Jii C 2 9.510.6 36 17.310.6 27 27.810.1 27 11.410.2 27 8.210.0 27 18.310.0 27 30.610.3 27 1810.1 (8.8-9.8) (15.0-18.0) (27.7-28.0) (11.3-11.9) (8.1-8.2) (18.3-18.5) (30.5-31.5) (17.8-l' pahos/cm 2 227+4 36 307+4 27 354+1' 27' 366+7 27 335+0 27 321+2 27 393+1 27 372+10 at 25 C (225-231) (296-314) (350-357) (345-371) (None) (320-325) (389-394) (370-42J l! Do 2 9.910.2 36 6.110.5 27 7.2+0.2 27 8.9+0.2 27 11.2+0.3 27 6.8+0.2 27 7.4+0.4 27 7.140.] I (9.8-10.1) (5.5-7.4) (6.9-7.7) (8.5-9.2) (10.4-11.8) (6.4-7.1) (6.9-8.3) (6.9-7. pH 2 7.7-8.2 9 7.3-7.5 27 7.7-7.8 27 8.1-8.2 25 7.9-8.0 27 7.8-7.9 27 7.5-8.4 27 7.6-7.t Total 1 0.5+0.1 9 0.2+0.3 9 0.310.4 9 0.410.2 9 0.410.2 9 0.210.3 9 0.410.2 9 0.410.: 4 J P0 (.09-0.9) (0.0-0.9) (0.0-0.9) (0.1-0.9) (0.1-0.9) (0.0-0.9) (0.0-0.6) (0.2-0.7 x0,.. 2

0. e_.0.1 9 0.410.1 9

0.1_.0.0 9 0.4_.0.1

0.,.0.1 0.,.0.0 0.5 0.1 0.4 0.:

(0.4-0.6) (0.3-0.7) (None) (0.2-0.5) (0.8-1.0) (0.9-1.0) (0.4-0.6)

0. 3-0. ti i

Turbidity 2 129114 0 9 57+15 9 201+21 9 144122 9 234119 9 60125 9 112120 JTU (112-137) (32-86) (168-228) (104-172) (197-258) (39-123) (80-13u HCO3 as 2 7413 8 115+6 9 136+6 9 116+8 9 93+2 9 94+2 9 166+7 9 130+3 I CACO 3 (70-76) (104-120) (128-144) 110-136) (90-96) (90-96) (154-174) (126-134 ( I; I 1 4 1; l e m +

.: 1 O

O G ~ \\

4 15 1 l Table 3. Diel i ariation in selected physicochemical characteristics of lower Mississippi River (Transect V, mi. 262.9) near St. Trancia-a l ville, Louisiana, August 27-28, 1974. I East Shore Mid s t ream West Shore Characteristic Time Surface Mid Bottom surface Mid Bottom Surface Mid bottom 1700 28.0 28.0 28.0 28.1 28.1 27.9 28.1 28.0 27.9 j 2000 28.0 27.8 27.7 28.0 27,9 27.8 28.0 27.9 27.9 2400 27.9 27.8 27.8 28.0 27.8 27.8 27.7 27.7 27.6

C 0500 28.0 28.0 27.0 28.0 28.0 27.8 27.8 27.7 27.5 1

0700 27.9 27.8 27.7 27.9 27.8 27.7 27.6 27.6 27.6 'k'j 1100 27.8 27.8 27.7 27.6 27.6 27.6 28.0 27.8 27.8 .t [j 1600 27.9 27.8 27.8 27.8 27.7 27.7 27.8 27.7 27.7 1j( 1700 7.2 7.2 7.4 7.3 7.3 7. '5 7.5 7.5 7.6 2000 7.2 7.3 7.5 7.1 7.2 7.4 7.3 7.4 7.5 II 2400 7.2 7.2 7.4 7.1 7.2 7.4 7.2 7.3 7.4 l DO g mg/l 0500 7.1 7.1 7.3 7.1 7.2 7.o 7.1 7.2 7.4 0 0700 7.1 7.2 7.5 7.1 7.2 7.6 7.1 7.2 7.4 1100 6.8 6.8 6.8 6.9 6.7 7.0 7.9 7.9 8.2 1600 6.9 6.9 7.1 6.9 6.9 7.0 7.3 7.2 7.4 il 1700 7.75 7.75 7.75 7.75 7.75 7.75 7.85 7.85 7.83 2000 7 75 7.75 7.75 7.75 7.75 7.75 7.77 7.82 7.80 d 2 2400 7.75 7.75 7.75 7.75 7.75 7.75 7.80 7.78 7.78 l pu 0500 7.75 7.75 7.75 7.77 7.75 7.75 7.79 7.77 7.77 h l 0700 7.75 7.75 7.75 7.75 7.75 7.75 7.78 7.78 7.78 y 1100 7.75 7.75 7.75 7.75 7.75 7.75 7.79 7.75 7.75 l 1600 7.78 7.77 7.77 7.80 7.75 7.77 7.85 7.80 7.80 y 1

I I I i i I I I I I I I I I I I I I L./ %./ L.) Table 4. East to vest variation in selected physicochemical characteristics of lower Mississippi River water samples taken near St. Francisv111e, Louisiana from January, 1974 to December, 1975. Units are mg/l unless otherwise indicated. East Shore Stations Midstream Stations West Shore Stations Characteristic n mean i sd (range) n mean i sd (range) n mean

sd (range)

C 72 18.610.2 (8.2-30.5) 75 18.31,0.2 (8.1-30.5) 72 18,710.3 (8.2-31.5) ymhos/gm 72 345110-(296-394) 75 352110 (225-394) 72 344110 (298-421) at 25 C DO 72 7.610.2 (5.6-11.8) 75 7.710.2 (5.8-11.7) 72 "7.710.2 (5.5-11.7) pH 61 (7.6-8.4) 64 (7.5-8.4) 61 (7.6-8.3) 23 0.310.4 (0.0-0.9) 26 0.619 5 (0.0-1.0) 23 0.31,0.3 (0.0-0.9) Total PO4 0.510 1[ (0.1-1.0) 26 0.610.1 (0.1-1.0) 23 0.Qto.1 (0.1-1.0) NO3 *N 23 Turbidity JTU 18 142120 (49-250) 21 127117 (39-258) 18 1321,19 (32-228) HCO3 23 11Qt5 (90-170) 26 11416 (70-166) 23 12215 (90-174) as. CACO 3 e -D m

i 1 I i l I i i I i l i I i i l O l-O.. I O Table 5. Downstream variation in selected physicochemical characteristics of lower Mississippi River water near St. Francisville, Louisiana, January, 1974 to l December, 1975. Units are mg/l unless 6therwise indicated. l Transect III (mi. 260.8) Transect IV (mi. 261.9) Transect _ 'J (mi. 262.9) n mean i sd (range) n mean i sd (range) n mean i sd (range c 75 18.513.0 (8.2-31.0) 66 18.712.0 (8.2-31.5) 77 18.312.0 (8.1-31.5) _umhos/cm. 75 334110 (302-394) 66 32717 (296-393) 77 -340115 (225-421) at 25 C l Do 75 7.510.3 (5.7-11.7) 66 7.810.2 (5.5-11.3) 77 7.410.2 (5.6-11.8) l pH 63 (7.6-8.2) 66 (7.6-8.2) 77 (7.1-8.4) Total PO4 24 0.510.1 (0.2-1.0) 21 0.310.3 (0.0-0.9) 26 0.310.2.(0.0-1.0) NO3 *N 24 0.510.1 (0.1-1.0) 21 0.510.1 (0.1-1.0) 26 0.410.1 (0.0-1.0) l Turbidity 18 129_+20 (49-245). 18 136115 (39-258) '20 138115 (32-250) JTU HCO 22 121+8 (90-174) 21 116+6 (90-168) '26 117+7 (76-174) as bCO 3 c 6 m

1{ 4 L Table 7. Seasonal variation (mean i standard deviation, range) in selected I physicoche2nical characteristics cf Alligator Bayou water samples taken January, 1974 through December, 1975. Data from all stations are combined; units are ug/l unless indicated otherwise. I 1975 1974 January - April - July - October - January - April - July - October - Characteristics n March n June n September n December __ n March n June n September n December I f

C 1

12.2 2 20.0+1.0 3 24.5+1.4 3 11.6+1.2 5 16.6+3.4 6 18.9+0.2 5 27.2+1.6 4 20.8+1.3 (19.8-21.2) (23.5-26.0) (10.5-12.8) (12.5-21.0) (18.5-19.0) (25.5-29.0) (19.0-22.0) f l i pahos/cm l at 25'c 1 144 2 88178 3 140148 3 107121 5 146137 6 1681115 5 125131 4 115134 l (150-160) (105-195) (90-130) (110-205) (40-295) (87-159) (89-165) I DO 1 5.8 2 2.510.7 3 4.512.3 3 8.512.3 5 4.8+3.4 6 7.9+0.3 5 3.5+2.2 4 5.1+2.2 (2.0-3.0) (1. 9-6.2) (5.9-10.3) (0.2-8.3) (7.5-8.3) (1.2-5.9) (2.1-7.7) pH 1 7.5 4 (6.9-7.1) 3 (6.6-6.8) 3 (6.5-7.1) 5 (6.6-7.0) 6 (6.7-7.6) 5 (6.5-7.1) 4 (6.9-7.2) i PO 1 0.9 3 0.2+0.3 3 0.6+0.4 3 0.110.0 3 0.5+0.2 3 0.1+0.2 4 0.3+0.2 3 0.4+0.2 Total l (0.1-0.5) (0.5-0.9) (0.1-0.1) (0.2-0.6) (0.5-0.3) (0.T-0.7) (0.T-0.2) 4

N 1

0.1 3 0.110 3 0.0+0.0 3 0.110.0 3 0.1+0.0 3 0.6+0.5 4 0.2+0.1 3 0.1+0.0 NO3 (0.1-0.2) (0.0-0.05) (0.1-0.2) (0.1-0.1) (0.2-1.2) (0 1-0.3) (0.1-0.2) Turbidity 1 92 0 3 120118 3 100152 3 88114 3 3111165 4 81161 3 108114 l l (106-140) (54-157) (80-104) (164-490) (38-172) (99-125) JTUs HCO-as 1 56 3 1615 0 3 4516 3 55+23 3 o+37 4 68+25 3 62+30 3 (10-20) (42-52) (36-80) (9-82) (52-106) (42-96) CACO 3 I l l I I O G. 9 om-en +e

l. ~ 20 i ( i (/ Table 8 Seasonal variation in (mean i standard deviation and range) Crant's Bayou water samples taken October,1974 through December 1975. Data from two stations are combined; units are sg/l unless indicated otherwise. I w 1974 1975 October - January - April - July - October - characteristic n December n M:rch n June n Sept eraber n Dece:nber ~ 'C 2 17.6+1.6 2 14.9+2.6 2 23.3+1.7 2 27.240.3 2 22.8+0.4 (16.5-18.7) (13.1-16.8) (22.1-24.5) 7 (21.0 27.5) (22.5-23.0) pahos/cm at 25'c 2 85+21 2 98+4 2 59+23 2 6713 2 168111 (70-100) (95-100) (43 75) (65-70) (160-175) e Do 2 6.3+2.9 2 9.8+3.9 2 7.2+1.1 2 6.2+d.9 2 4.2+0.8 (4.2-8.4) (7.0-12.6) (6.4-7.9) (5.5-6.9) (3.6-4.8) pH 2 (7.4) 2 (6.6-7.0) 2 (6.4-6.6) 2 (6.2-6.5) 2 (6.4-6.7) ? Total N 2 0.1+0.02 2 0.25+0.21 2 0.85+0. 07 2 0.65+0.21 2 0.2010.00 4 (0.09-0.12) (0.10-0.40) (0.80-0.90) (0.50-0.80) (0.20) NO

N 2

0.0M_0.02 2 0.0510.04 2 0.1810.02 2 0.1410.02 2 0.1210.04 3 (0.05-0.08) (0.00-0.10) (0.17-0.20) (0.12-0.15) 0.10-0.15) Turbidity 2 11818 2 5213 2 1215 2 17013 2 8.414 J1V (112-123) (49-56) (49-56) (168-172) (81-86) p/ nc03 as 2 26il 2 3811 2 2911 2 2811 2 73127 cac03 (25-26) (37-38) (28-30) (28-29) (54-92) I w l J = 4 w f e., es. 6 N k-w)

21 (~h jv PHYT,0 PLANKTON Mississippi River ~ From January 1974 through September'1975, over 100 taxa of phytoplanktou were recognized in 133 samples from the St. Francisville reach (Table 9). Nine algal groups have appeared in more than 75% of all samples in the 1974-75 collections and were also common in 1972-73 samples. As in past studies chlorophytes were most diverse and less abundant relative to the Chrysophyta and Cyanophyta. There were 48 chlorophyte taxa, 35 chrysophytes, 11 cyanophytes, ~ five euglenophytes and only three pyrrophytes. Anacystis, Cyclotella, Melosira, Scenedesmus and Chlorococcales appeared in order of decreasing cell caunt abundance in 1974-75 seasonal samples : (Table 10). All algae were especially numerous during the summer sampling _ 7_ periods, particularly members of Cyanophyta and Chrysophyta. However, the diatom Cyclotella was nearly twice as abundant in Winter 1975 as in any other season during the study pericd. The green alga Scenedesmus apparently is favored by low discharges and warm water. conditions, whereas the unidenti-fiable green coccoid forms of Chlorococcales were more seasonally dispersed. Similarly, the diatoms Navicula, Synedra and Fragilaria appeared in rather consistently low numbers throughout the study period. That there can be local sites of increased primary production of the lower Mississippi River is appaccat from data in Table 11. During low ~~ discharge waters on the west shore were demonstrably more productive of phytoplankton than midstream or cast shore waters, especially during the 24-hour study in August 1974. Samples taken during the Summer 1975 O _v Mr

22 corroborate this conclusion as do the water quality data. ~ Alligator Bayou The similarity in order' of frequency of appearance (except 'A acystis) of phytoplankton in Alligator Bayou with that in the River is a reflection of the influence of latter on the aquatic communities of this sump area (Table 12). The " normal" surface of Grassy Lake (sampling area) was lower than stages above mean sea level recorded for the river at Bayou Sara gage from early December 1973 till the middle of May 1974 and again from the last of May till early July 1974. During 1975 the river directly influenced stages in Grassy Lake from early February till early June. Although periodic " blooms" in p 'nkton algal growth might be expected, especially following recession of floodwaters, we have not witnessed such growths. Indeed, the greatest numbers '() have been seen in samples taken during the height of river influence. This may be a consequence of the usually high turbidities and/or profuse bordering canopy-which influence light penetration during lower river stages. Moreover, water quality data show that certain nutrients, especially nitrates were i usually rapidly depleted in this system after water temperatures exceeded 20*C. w ..-.,E-

23 p_.x \\ Table 9. Frequency of appearance of algal genera appearing in 176 phytoplankton samples from the lower Mississippi River near St. Francisville, Louisiana from February, 1974 through November, 1975. Frequency of Occurrence in Samples Taxon >75% 75-50% 49-25% <25% Chlorophyta Chlorophyceae /' X Chlamydomonas Volvocales X Volvox X ~ Pandorina X Tetrasporales X Sphaerocystis X Glaocystis X l Ourococcus X Binucleria X Chlorococcales X Golenkinia X X Dictyosphaerium Characium X Schroederia X Pediastrum X Coelastrum X ~ n J Chlorella X 'X Planktopshaeria 00 cystis X

24 I Table 9. Continued. O Frequency of Occurrence in Samples Taxon >75% 75-50% 49-25% <25% X Ankistrodesmus 'X l Franceia X Closteriopsis .X Selenastrum X Kirchneriella_ X Tetraedron f. Scenedesmus X Crucigenia X X Tetrastrum ._q X k,) Actinastrum. X Spirogyra X Desmidiaceae I y ~ Closterium .X Cosmarium X Micrasterias X Penium X Staurastrum X l Hyalotheca X Tetradesmus X Micractinium X Lagerheimia ~ X h Chlorosarcina X Treubaria 4 g

Y 25 i Table 9. Continued. ~~ Frequency of Occurrence in Samples Taxon >75% 75-50% 49-25% <25% Ulothrix

I Eudorina X

Euastrum X Spondylosium X X Arthrodesmus Pleodorina X Euglenophyta Euglenophyceae X Euglena X Lepocinclis X ~ Trachelomonas X Chlorogonium X Chrysophyta l, Xanthophyceae Ophiocytium X Dinobryon X Bacillariophyceae X Synedra X g Asterionella X Achnanthes X Cocconeis X t Tribonema X [ ~~ ~ \\ Cyclotella* X ^ Stephanodiscus X

~

f . ~

26

Table 9.

Continued. O Frequency of Occurrence in Samples-Taxon >75% 75-50% 49-25% <25% d' Coscinodiscus X Tabe11 aria X Meridion X Navicula X Pinnularia X- ~ X Gyrosigma Comphonema X / 'X Nitzschis Melosira 'X Fragila'ria X Surirella X 1 Cymbella .XI .I Stauroneis Diatoma X .Eunctia X I Hantzschia X - ~ l .X Centritractus I' X f ~ Opephora Mastoglia X 'Rhopalodia X l-Brebissonia X i ~ Frustalia X Rhoicosphenia X i I e

i* 27 Table 9.. Continued. O 1-Frequency of Occurrence in Samples I"*'" >75% 75-50% 49-25% <25% X Cymatopleura i Amphora X Pyrrophyta ~ Dinophyceae i Glenodinium X 'l l. Gymnodinium X Ceratium X f-Cyanophyta ~ / ~ Myxophyceae Chroococcales X ~O X Dactylococcopsis l ~~ Anacystis X l-Coccochloris I i-l l Agmenellum .X t Comphosphaeria X Spirulina X Oscillatoria X '~ i Phormidium X i Anabaena X Hormogonales X i i w r O S g

I I i l l I I I i ,I I I i i [ t t, .I q 0 i) ) Tcble 10. Seasonal variation in the ten most frequently cccurting phytrplcnkton g'n ra in tha lower Mimicaippi River near St. Francisv111e, Louisiana from January 1974 through September 1975. Samples from All stations are combined; average nu=ber of cells per liter, standard deviation and range are presented. 1974 1975 January - April - July - October - January - April - July n March n June n September n December n March n June n Septe=ber ,Cyclotalla 2 27120 18 7251309 60 845i632 15 5981879 18 15451425 9 5191427 11 8771263 (13-41) (235-1270) (124-2402) (10-2323) (687-2452) (78-1141) (521-1318) shloreccccales 2 1311 18 32126 60 210+194 15 701123 18 114142 9 1931133 11 253171 (13-14) (0-80) (15-1003) (0-387) (40-200) (0-386) (107-350) Anacystis 2 207 138 18 1331130 60 7459143470 15 4931840 18 931114 9 1831448 11 233512378 (110-305) (0-434) (0-316291) (0-1881) (0-352) (0-1282) (0-6274) N:vicuin 2 7110 18 55136 60 50146 15 21129 18 53138 9 67194 11 40126 (0-14) (0-114) (0-177) (0-101) (14-154) (0-241) (8-98) Melonirn 2 34+49 18-616+287 60 1125+731 15 382+570 18 134+95 9 192+209 11 1010+415 (533 1888 T (19 363) (0-657) (O 69) (159-1101) (87-2621) .(9-1680) I-Syn-dra 2 7110 18 84161 60 50154 15 18128 18 42134 9 36138 11 70154 (0-14) (14-212) 10-205) (0-70) (0-100) (0-104) (10-175) scened smus 2 0 18 56+42 60 454+253 15 173+247 '18 50+55 9 68+112 11 470&l48 (0-155) (0-941) (4-830) (0-200) (0-309) (246-730) Frenil ria 2 7+10 18~ 29+40 60 59+123 15 11+18 18 82+82 9 48+38 11 21+18 (0-14) (0-139) (0-905) (0-69) (0-303) (0-104) (0-64) Chrencoccales 2' 8614 18 24139 60 1461115 15 46196 18 391105 9 34152 11 190191 (82-89) (0-117) (0-362) (0-377) (0-440) (0-150) (49-313) Eugl na 2 619 18 6112 60 16118 15 14125 18 64147 9 35143 11 8110 (0-13) (0-49) (0-82) (0-73) (0-172) (0-138) (0-30) Totsi 2 717143 18 22651657 60 13042+41101 15 270413360 18 30651619 9 220911046 11 827912257 phytoplankton (686-747) (1280-3419) (982-324528) (309-9184) (1893-4644) (731-3776) (5454-1168 E$ ~

I I I I I ( l i I I l l 1 1 I I i i l O O O i Tabl& 11. East to west variation in total phytoplanktom cell estimates in the lower Mississippi River near St. Francisv111e, Louisiana. Data from all transects are combined; units are cells per liter. 1974 1975 April - July - October - January - April - July - n March n June n iSepte=ber December} Station n June n September n East Shore 6 289130 21* 7041257 9 5391196 ' 6 350184 3 221140 3 10021185 (258-340) (264-1145) (302-816) (247-460) (194-267) (815-1185) Mid-River 6 299+40 15* 742+375 3 410+158 6 343+41 3 236+33 3 '1048+319 (234-348) (240-1623) (296-590), (285-412) (212-273) (707-1339) West Shore 6 328+51 15* 1936F5028 3 373+51 6 325+36 3 234+25 3 ~ 12404-423 (250-375) (231-20093) (332-430) (286-383) (208-258) (875-1703)

Includes'24-hour study on August 27 4. 28, 1974.

9 e i \\. e 4 e d M gens

I I,.s I ' l' I I i l I ,) I l I I I I - 1 O O -) Tcble 12. Seasonal variation in ten most abundant phytoplankton genera-in Alligator Bayou near St. Francisville, Louisiana from January, 1974 through September 1975. Data from all stations and transects are combined; units are cells per liter. 1974 1975 January - ' April - July - October - January - April - July - Tnxon n March n June n September n December n March n June n September Cyclotella 6 24+16 6 304+302 6 30+24 3 27+30 8 65+115 3 73+82 3 24+25 (14-55) (14-826) (0-60) (0-60) (0-344) (0-161) (9-53) Chlorococcales 6 23+50 6 68+37 6' 128+92 3 27+11 8 170&88 3 172+50 3 95+42 2 (20 40) (662288) ~ (117 215) 7d!144 (0 124) (38 272) (15 123) Navicula 6 53+66 6 290+164 6 160+10S 3 47+30 8 83+46 3 88+79 3 10l+68 (0-180) (0-459) (47-2'-) (20-80) (30-176) (27-176) (40-174) Melosira 6 7+17 6 356+308 6 23+30 3 0 8 11+28 3 83+81 3 0 7 2 (0 750) (0 76) (0 79) (0 46) (0 161) Synedra 6 67185 6 3061187 6 60t16 3 34 12 8 76163 3 0 3 28122 (0-235) (123-551) (47-85) (20-42) (0-202) (10-53) Scenedesmus 6 61+119 6 509+430 6 89+83 3 0. 8 120+54 3 54+93 3 48+46 T (97 1063) (62221) T (60 230) (0 303) (0 161) (O 91) Fragilaria 6 16119 6 84+84 6 74+63 3 56+96 8 48+S9 3 59+77 3 68+74 (0-46) (0-225) (0-152) (0-167) 0-176 (0-147) (10-151) Chroococcales 6 77+86 6 0 6 85+42 3 20+1 8 82+79 3 92+107 3' 42+30 T 2 2 2 (10 70) (42 136) (19 21)- (9 220) .(29 214) (0 198) Euglena 6 0 6 876+840 6 88160 3 0 8 34128 3 0 3 15114 (28-2050) (0-172) (0-74) (0-26) An cystis 6 2331227 6 59148 6 52144 3 27 46 8 9+14 3 0 3 16t15 (0-608) (0-107) (0-121) (0-80) (0-38) (0-30) Tatc1 6 3861172 6 4841198 6 308163 3 3381134 8 328181 3 293161 3 262138 (174-600) (253-725) (241-369) 184-428 205-439 (252-363) 222-297 o

31 i i MACR 0 ZOOPLANKTON AND DRi'T Qualitative Composition [,:

"i g Animals collected 'in 0.505lmm mesh. meter-net. tows may be assigned.,to two categories on the basis of their mode of life -- namely, the truly planktonic forms, or euplankton community, and the drif ting benthonic forms, or drif t community. Taxonomic composition and overall relative abundance of the various componento of these communities in two habitats are summarized in Tables 13-16. Distinction is made between the two communities because meter-netting experience near Grand Gulf, Mississippi,

~ revealed that catches of' drift animals were significantly higher at night than in daylight tows while night versus day collections of truly plank-tonic forms were not markedly different (Bill McConnell, personal communi-() With the exception of one 24-hour study in August,1974, al'1 cation). meter-netting at River Bend was done during daylight hours. ~ In comparing the catches / effort and diversity of Mississippi River g versus lower Bayou Sara samples it should be noted that the former habitat is represented by almost two years of monthly and semimonthly collections whereas the latter is represented by only six and a half months of ~ i collections from one year (1975). In terms of overall catches / effort microcrustaceans (cladocerans, copepods) dominated the cuplankton~ communities and insect larvae (especially dipterans, mayflies, caddisflies) dominated the drift communities of both the Mississippi River and lower Bayou Sara. Unless otherwise indicated the following remarks pertain to both habitats. ) Among cuplankters certain species were present virtually year-round and were usually responsible for temporal peaks of abundance within their ~ i t

32 respective groups: Daphnia parvulai D_. pulex, Simocephalus serrulatus (Cladocera, Daphnidae);.Mesocyclops 'edax (Copepoda, Cyclopidae); and phantom midge pupae (Insecta, Diptera, Chaoboridae). Other species were seasonally quite abundant:. 'Holopedium'amazonicum (Cladocera, Holopedidae); Sida crystallina, Diaphanosoma spp. (Cladocera, Sididae);'Ceriodaphnia spp., Scapholeberis kingi, Simocephalus exspinosus, Moina spp. Cladocera, Daphnidae); Eurytemora affinis (Copepoda, Temoridae); Diaptomus spp. (Copepoda, Diaptomi. dae); Cyclops _vernalis,_C_. bicuspidatus (Copepoda, Cyclopidae); river shrimp larvae (Decapoda, Palaemonidae -- mainly in river); gizzard and threadfin - shad larvae; river carpsucker larvae (mainly in river); crappie and sunfish larvae (mainly in bayou); and freshwater drum larvae and eggs (mainly in river). Phantom midge larvae were the only drift animals taken year-round, ._,O although seasonal and/or local peaks in abundance were apparent for other ~ major drif t forms: fragments of hydroid colonies; oligochaetes; burrowing mayfly nymphs (especially Tortopus primus in the river); and caddisfly larvae (especially Hydropsyche orris in the river). Taxonomic differences in the euplankton communities observed in the river versus bayou samples were very slight, involving r;nly forms of infrequent occurrence and low overall densities (e.g., opossum shrimp and certain fish larvae, taken in river only). In terms of overall catches / effort, however, it may be seen '(Table 14) that euplankton densities tended to be somewhat higher in the bayou. Most pronounced differences involved greater bayou catches of cladocerans (holopedids, sidids, daphnids); ~ copepods (especially diaptomids); and certain fish larvae (clupcids and centrarchids). River collections, on the other hand, yielded more river .--.-s

33 ohrimp larvae, dipteran pupac, sucker larvae, and drum larvae and eggs. i Composition of the drift communities differed much more, taxonomically, and less, in terms of overall catches / effort, between river and bayou habitats than did that of the euplankton (Table 16). Certain minor groups, such as nematodes, leeches, young clams, ostracods, springtails, and odonates appeared only in river sampics. All of these are undoubtedly represented in the benthos /aufwuchs communities of Bayou Sara -- probably for the most part in greater densities than in the river -- but the virtual lack of turbulence may partly explain their absence from bayou samples. The contrsst may also be an artifact of not having sampled the bayou in late summer and winter, periods during which the cited groups were most frequently cncountered-in river collections. SeveralgroupswererLlatkvelymore ~~ abundant in one habitat than the other: hydroids (river); snails (bayou); I branchiurans (bayou); amphipods (river); mayflies (river); hemipterans (bayou); caddisflies (river); beetles (bayou); dipteran larvae (river); and water mites (bayou). It should be noted that among mayflies the predominant I species in the river were ephemerids, or burrowing types (Tortopus primus, l etc.), while in the bayou sprawling types (Caenidae, Baetidae, Heptageniidae) predominated to the virtual exclusion of burrowers. %d .mu. Y r - t) ese

e 34 l (s'/ Seasonal Patterns of Relative Abundance ) l s-Overall catches / effort and diversity of euplankton and drift in the river tended to be highest in the spring and summer and lowest in autumn and winter (Tables 17 and 18; Figs. 3 and 4). Among cuplankters, cladocerans (mainly daphnids) tended to dominate c'atches through spring into early summer, when moderate to low river stages obtained. Then, for one or two months (depending upon the year) copepods were numerically dominant, ~ followed by a brief resurgence in the relative ab'undance of cladocerans. This late-summer pulse of cladocerans reflected apparent " blooms" in the populations of Daphnia parvula, a year-round contributor, and Moina spp., forms whose occurrence in the river was virtually confined to warmer, low-stage periods. Cyclopoids (especially Mesocyclops edax) dominated the

O) summer and autumn catches of copepods, while calanoids (especially Diaptomus

(, spp. and Eurytecora affinis) tended to be relatively more numerous in the winter and early spring. I Meaningful enumeration of the sessile forms, hydroids and entoprocts, was difficult since the quantities of ' coarse detrital material in samples dictated variable procedures for their handling, which in turn might have in'fluenced the extent of fragmentation of colonies (one piece, however large or small, was taken as a unit in our counting procedure). Therefore distinction was made between total drif t and drif t minus sessile forms (Tables 18 and i 20; Figs. 3 and 4). As noted above, the drif t was dominated by the larvae and adults of insects which, in turn, consisted primarily of dipterans (especially phantom {~} midges). ' The late spring and summer peaks in abundance of drift also ,J reficcted increased numbers of mayflies, hemipterans, caddisflies, and

36 ~ ) % s' ._m ~ EUPLANKTON O onta twLumTom a Coptroos D CLADoCInANs ~ 10000 - ,s sooo. ~ C 4000-w i i ~ g o sooo- 'i J d l

9

~ l l a-W 2000 - l 4 P' g i I i n = I j b$j":d j il a u e a

l

= a ,oo. i i E NsECT LAnvAt & ADiifs -12 O onentwT -ss e "o

~

DRIFTtNG BENTHOS -8 G (wes stsstt ronus -e m b So - g 5 g 5 I .s g . g so. ~* g no- -s s 10 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC l Figure 4. Catch / Effort of macrozooplankton and drif t in 0.505 c:m mesh meter-net tows at Mississippi River Station V-A (above proposed l River Bend intake area), 1975. W k I a,s l l l 9 l

37 beetles. In general, these last-mentioned groups were represented in about equal proportions during the spring and early summer', while mid-to late- ~ summer catches were dominated by mayflies (especially Tortopus' primus) and caddisflies (especially Hydropsyche orris). Major contributors to the drif t other than insects were oligochaetes (especially during high river stages) and crustaceans (isopods and amphipods during high-water, amphipods alone during low-water). 24-hour Study and Horizontal Distribution In an earlier report it was noted that, under low-flow conditions, larger zooplankters and drift animals tended to be most abundant along the eastern shore (Station A), slightly less abundant at midstream (C), and least abundant along the western shore (E) across river Transect V. These differences were believed to be associated primarily with relative turbulence, which varied from high (surface currents of 50-80 cm/sec along eastern ~ shore) to very low (0-10 cm/see along western shore) under late-summer conditions. Rationale was that in less turbulent water the animals would be better able to avoid the net and/or would be more likely to be stratified vertically as zooplankters often are in lentic environments. If net avoidance, vertical stratification, and/or any other behavioral phenomena associated with diel variations in environmental conditions were affecting our meter-net catches, they would likely be manifested in a i 24-hour sampling exercise. Accordingly, on 27-28 August 1974 we made meter-net tows at roughly 4-hour intervals at the three stations across Transect V. Tables 19 and 20 and Figures 5 and 6 depict the results of this dis 1' study (see also the water quality section). ' p There were indeed diel dif ferences in the meter-net catches and, as d l i r l ~ l

a 35 O ~ Moco - EUPLANKTON O oTan ttsuiciom 8 CN uooo-3974 E cLaoocta ms toooo - sooo-P 6000-i e p 4000 h lI 1 - q e P e e==- n i 3 j "l E ~ <l l m a-9 a a j j i llj l ~ i] f { ,,0 t G NstcT i.AnvAt a Atxits 1 -O b h 0 i O oTER DRFT (J-n I a 4 e s 4co- -11 o t m DRIFTING BENTHOS g -e (wos stsstt roms) e-w so. 7 i ~ g 30 5 w y g e e -4 W ii 20 - = io _ JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC l-Figure 3. Catch / Effort of macrozooplankton and drift in 0.505 cm mesh meter-net tows at Mississippi River Station V-A (above proposed River Bend intake area),1974. a

38 /*% I ) ,V w DRIFTING BENTHOS u C3 HYDROC & LN10f90CT FRAGMD(15 f O OTHER DRFit4G BCNTHOS (,' MAYFLY NYuPh5 240- [2] DtPTERA LAAVAE (MAftY CHA000 pus) l$ fii M N i, I.., k', I?; s ['* "ij m2 18 0 - u g f t.D-L' (;;. I f rA 7 i 1 fj f' +" 5 1 ,c W W ~ f .1- ") O 120 3 -Q Z l J w 1 y'yd f W e d - 6 ...? m e 60-Q t 3 u..,.e e-tw ..s,"'o t,, 'm 7 ma -= t g,, f, w ~ C i;h 49 1:i ..g 4 EL N. 3 MiJ W Q+$ ~ c j{

t. ll

';c i,.;f_ _. e 7 _. %.. i! t ?1 . $.D in ~u~ ~ itis 2035 2345 usoo 0720 $200

isas,

/ ( EUPLANKTON (/ ( u n Sao-u ~ b O OTHER EMANKTON I.1_ In cortPODS r-cza ctAoottRANS I ,m 2mo-r,t t g I n r. t E o t r ..s . I, 1 o u, a s. 1 g ",) 4 u O d w ..g ,,j g g-z ,1 f-g L. i .v ~; t ,~ w - w . 9 . m -""1 l 7 2 .osoo 0720 2% E0 l ~ ns 2035

11; l

i I l Figure 5. Catch / Effort of drift and macrozooplankton in 0.505 mm mesh noter-net tows during dici studies at stations across Mississippi River Transect V, 27-28 August 1974. (E = east shore; M = mid-O stream; W = west shore) 5~) 959 i t I l

i. 39 FISH LARVAE & EGGS CJ ontarwes so. am m ows e sucxces Q no-M DRUM r" c w g u. =b yn1. . h. un aun n< 5 om one uw mo w w t ~- 4 DPTERAN PUPAE no. S so ^x" { no: 1 ~ x 1 y q h ,4"1 w ~ bw r f"1w i w m3

a

r.n us*

as aia no i RIVER SHRIMP LARVAE no-L L { L L 1 L g 1 u' u y 40-1 1 g W w L w I. E l b _W_ 2635 _ 2345 u50(i u720 .20 J 42iJ JIS. Figure 6. Catch / Effort of selected macrozooplankters in 0.505 mm mesh . meter-net tows during diel studies at stations across Mississippi River Transect V, 27-28 August 1974. (E = cast shore; M =.mid-stream; W = west shore) 9 1

40 j/N e:cpected they were much more pronounced in the slackwater area (along western shore), catches of total euplankton, on the aver. age, were about 1.7 to 2.3 tLmes as great at night in the eastern shore and midstream stations while the night versus daylight ratio in the western shore station was about 11:1. For drift minus sessile forms the night: day rations were 1.5:1 for the eastern shore, 1.1:1 for midstream, and 4.3:1 for the western shore. It is also apparent, however, that the diel variations in horizontal ~ distribution differed according to the taxa considered. Extremes are reflected by river shrimp larvae, whose catches / effort and horizontal patterns scarcely differed from one sampling period to the next; and dipteran pupae, which were absent from daylight samples.taken in the () slackwater area yet more abundant there at night than in other stations. Fish larvae and eggs showed rather remarkable temporal and spatial patterns during the 24-hour study. Midday and late-afternoon catches I were all very similar and exhibited the tendency toward east-west decline in abundance across the transect. At night and inmediately af ter dawn, however, ichthyoplankters tended to be more numerous along both shorelines than at midstream. Slightly greater overall abundance of ichthyoplankton obtained during the predawn and postdawn sampling periods, reflecting the occurrence at those periods of roughly equal proportions of cyprinoid I ~ larvae (minnows and suckers) and drum larvae and eggs During the remainder of the 24-hour cycle cyprinoids tended to predominate night catches while drum tended to predominate in midday and late-afternoon tows. O _G 9

41 Ichthyoplankton Although fish larvae and. eggs in, general did not contribute.very significantly to the overall cuplankton community (less than 1 percent, l on the average - see Table 14) they deserve some special discussion in view of the economic 12nportance of some species and the relatively greater popular interest in fishes. About 32 kinds of fish larvae and eggs have been recognized from ~ meter-net collections, of which about two-thirds have been identified to the species level (Table 13). Only a few forms were relatively abundant ~ in plankton tows: gizzard and threadfin shads; carp; thu'a (nybopsis spp.); shiners (Notropis spp.); river carpsucker; white bass; crappies; sunfishes ~ (Lepomis spp.); and freshwater drum. The shads, carp, white bass, crappies, and sunfishes were seasonally common in both river and bayou samples, but chubs, carpsuckers, and drum appeared almost exclusively in river collections. Temporal patterns of occurrence and relative abundance are shown in I ~ Table 17 and Figure 7. Ichthyoplankton first appeared in meter-net collections from late March and disappeared after September in both years. Earliest fish to appear in river collections were gizzard shad (Dorosoma cepedianum) while gizzard shad along with centrarchids (mostly crappies) were first to appear in Bayou Sara. Most shad larvae found after early May in both habitats f were threadfin (D_. petenense) and most centrarchids by early May were sunfishes (Lepomis spp.). l'atterns of occurrence and relative abundance of drum larvae and eggs tended to be bimodal, suggesting two major spawning peaks. First appearance of drum in both years was in early May, followed by a brief peak in numbers (late May in 1974, early June in 1975). A second. peak of v abundance was apparent in mid-to late-summer (ill-defined in 1974). Among ~

n RIVER a> p 1974 ~ W {' t -U T o 4o- ,v

s n

u 8 U b M-20-m w

j Q-n r,

mus _ RIVER 80-7 1975 . s. so- =2 40-6l 1 = v h y u 20- =- 4 g

,)

~ ~ pq C H h j P"E d O9 E 469 / E {M N too-a s lj BAYOU SARA F- ^ 1975 m D 160-(s) Z y 140-4- SHAD ~ SUNFISHES 120-M DRUM I t 4' OTHER FtSHES s ~ ~ .00-y m-s A .s e 40-8 8 fli;!! k t t-20-g qp;,: ,w w 3 d j!h ~ c,6 m m - - Mi 9 m up MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER Figtre 7. Catch / Effort of ichthyoplankton in 0.505 mm mesh meter-net tows /Q in Mississippi River Station V-A, 1974-75, and lower Bayou Sara, TJ 1975. 4 6 9

=. 43 ' the other fishes (unshaded portions of histograms, Fig. 7) the following .patthrus were observed: carp and white bass were the predominant forms in April and May; chubs and carpsuckers in early to mid-summer; and shiners in August and September. 4 m f ~ / O ad =*e i e l l I l, l l I l i O w een

45 Table 13. Continued. O t(_) Family Diaptomidae Diaptomus clavipes'Schacht D. birgei Marsh D. clavipoides Wilson D. dorsalis Marsh {[. louisianensis Wilson and Moore D. stagnalis Forbes- ((. reighardi Diaptomus spp. (about 3 unidentified forms) Order Cyclopoida - cyclopoid copepods - I Family Cyclopidae Cyclops vernalis Fischer (1. bicuspidatus thomasi Forbes CL. varicans rubellus Lilljeborg Cyclops spp. (about 2 unidentified forms) Macrocyclops albidus (Jurine) ji. fuscus (Jurine) Mesocyclops edax (Forbes) gI. inversus (Kiefer) Subclass Malacostraca ~ Order Mysidacea - opossum shrimps Family Mysidae Taphromysis louisianae Banner Order Decapoda - shrimps, crayfish, etc. ~ /"}' Family Palaemonidae - freshwater shrimps \\- Macrobrachium ohione (Smith) - river shrimps Class Insecta - insects Order Diptera - true flies (pupal stages) Family Tipulidae - crane flies Helius (?) sp. Family Chaoboridae - phantom midges Chaoborus sp. Mochlong sp. Eucorethra sp. Family Culicidae - mosquitoes Culex sp. Anopheles sp. 8 Family Empididae - dance flies Hemerodromia sp. Family Chironomidae - midges Chironomus spp. (about 3 unidentified forms) Cricotopus sp. Pentancura sp. (cf. carnea) Pentancura sp. (cf. flavifrons) Procladius sp. (cf. culiciformis) Corynoneura sp. Tanytarqus sp. unident.ified midge pupae (about 5 forms) Family Ceratopogonidae - biting midges g-)s .Bezzia ep. (_ 4 e O

47 3 (number /100 m ) in 0.505 mm (~'g Table 14. Summary of overall catches / effort ~^ / mesh plankton net tows in Mississippi River Station V-A ~ (above proposed River Bend intake) and lower Bayou Sara, 1974 and 1975. (Numbers in larger type are sums of the under-lying family entries.) Bayou V-A V-A Sara TAXA 1974 1975 1975 CLAD 0CERA - water ficas 1802.69 2046.08 125733.36 Leptodoridae 4.44 0.90 2.05-Holopedidae 91.39 86.68 728.76 Sididae 29.71 35.38 657.19 1676.30 1919.02 124323.79 Daphnidae Bosminidae 0.26 0.07 17.99 Macrothricidae 0.15 1.88 1.02 Chydoridae 0.41' 2'.36 2.66 COPEPODA - copepods 1025.71 908.95 10157.65 Temoridae 232.80 124.63 220.43 Centropagidae 3.13 3 61 3.17 Diaptomidae 189.77 298.05 8492.49 Cyclopidae 559.30 482.59 788.37 MYSIDACEA'- opossum shrimps 2.93 0.70 DECAPODA - shrimps, etc. 40.08 25.65 0.92 ~ b) DIPTERA PUPAE - midges, etc. 10.26 ~10.64 2.25 OSTEICHTHYES - fish larvae & eggs 18.58 27.80 126.16 Clupeidae - herrings, shad 9.29 10.08 113.63 i Cyprinidae - minnows 1.90 3.61 1.02 Catostomidae - suckers 2.46 5.07 0.31 Aphredoderidae - pirate perch 0.07 Poeciliidae - livebearers 0.05 0.08 Atherinidae - silversides Percichthyidae - temperate basses 0.10 0.42 0.10 Centrarchidae - sunfishes 0.56 1.04 8.08 Percidae - perches, darters 0.36 0.07 0.41 Sciaenidae - drums 3.75 7.16 0.20 3 MEAN TOTAL EUPLANKTON/100 M 2900.14 3019.81-135336.57 NUMBER OF TAXA (RANGE) 10-36 13-33 6-28 20.4 20.4 16.5 NUMBER OF TAXA (MEAN)3 84.7 84.6 88.9 MEAN SAMPLE VOLUME (M ) -p e

48 O Table 15. Systematic list of drifting benthonic animals encountered in 0.505 mm mesh plankton net collections from River Bend study area, 1974 - 1975. PHYLUM COELENTERATA (CNIDARIA) - jellyfish, corals, etc. Class Hydrozoa - hydroids i Family Clavidae Cordylophora lacustris Allman - colonial hydroid (fragments) Family Hydridae i Hydra sp. - colonial hydroid (fragments) PHYLUM NEHATA - nematodes unidentified nematodes (about 3 forms) '~ PHYLUM ENIOPROCTA - entoproct "bryozoans" Family Urnatellidae Urnatella g;acilis Leidy - colonial entoproct (fragments) PHYLUM ANNELIDA - segmented worms Class 011gochaeta - oligochaetes Family Naididae Stylaria lacustris (Linnaeus) unidentified naidids (2 forms) Family Tubificidae ~, s unidentified tubificids (2 forms) Class Hirandinea - leeches unidentified leeches (2 forms) PHYLUM MOLLUSCA - mollusks Class Gastropoda - snails, etc. Fmnily Physidae Physa sp. Family Planorbidae Helisoma sp. Family Lymnaeidae Lymnaea sp. Class Pelecypoda - clams, etc. Family Corbiculidae Corbicula man 11ensis (Philippi) - Asiatic clam (young) ( ~ PHYLUM ARTHROPODA - jointfooted animals Class Crustacca - crustaceans Subclass Ostracoda - seed shrimps (adusts) unidentified seed shrimp Subclass Branchiura - fish lice (young, adults) Family Argulidae Argulus spp. - fish lice (about 3 unidentified forms) O' Subclass Malacostraca Order Isopoda - aquatic sowbugs (young, adults) Family Asellidae Lirceus louisianae (Mackin and Hubricht) Order Amphipoda - scuds (young, adults) ' ~ Family Talitridae m

i 1 T:ble 15. -Continued. s_ l . Hyallela azteca-(saussure) .O. r 117 cammaridae Cammaris sp. Class Insecta - insects (larvae, adults) Order'Collembola - springtails Family Isotomidae .Isotoma sp. Family Sminthuridae 'Sminthurides sp. ' Order Ephemeroptera - mayflies 2 Family Ephemeridae - burrowing mayflies -l Tortopus primus (McDunnough) 1 ~ Pentagenfa_ vittigera (Walsh) Hexagenia limbata (Serville) Familt Caenidae ~ Caenis sp. Family Baetidae . unidentified baetid l Family Heptagen11dae j. Stenonema spp. (2 fc rms) Heptagenia sp. 4 i Order Odonata - dragonflies and damselflies -Suborder Zygoptera - damselflies i Family Coenagrionidae Enallagma sp. 2 tp Coenagrion sp. 3 v Suborder Anisoptera -'dragonflics Family Gomphidae l Comphus sp. Family Libellulidae 4 Libellula sp. -l9 Order Hemiptera - bugs Family Pleidae - pygmy backswimmers Plea sp. ~ Family Corixiidae - water boatmen Trichocorixa sp. unidentified corixiids (about 2 forms) Family Naucoridae - creeping water bugs Pelocoris sp. I Family Veliidae - broad-shouldered water striders j unidentified veliid b Order Megaloptera - alderflies, etc. Family Sialidae - alderflies Sialis sp. Order Trichoptera - caddisflies Family Psychomyidae Neureclipsis sp.

~

unidentified psychomyids (about 2 forms) Family Hydropsychidae Hydropsyche orris Ross j Cheumatopsyche sp. 4 Family liydroptilidae Hydroptila sp. (?) I i- ~ ,,.-n...,. ...m.-, ~.

50 . Table 15. Continued. A Family Leptoceridae %, / Leptocerus_sp. Order Lepidoptera - butterflies, moths, etc. Family Pyralidae - aquatic moths Synclita sp. Parargyractis sp. Order Coleoptera - beetlea Family Dytiscidae - predaceous diving beetles Hydroporus sp. Coptotomus sp. Dytiscus sp. Cybister sp. Laccophilus sp. Family Gyrinidae - whirligig beetles Dineutus sp. Cyrinus sp. Family Hydrophilidae - water scavenger beetles Hydrophilus sp. Tropisternus sp. Family Staphylinidae - rove beetles unidentified staphylinid Family Dryopidae Dryops sp. ~ Family Elmidae - riffle beetles Stenelmis sp. () unidentified elmids (about 2 forms) Family Chrysomelidae - leaf beetles Donacia sp. Family Curculionidae - we&vils unidentified curculionid r. Order Diptera - flies, mosquitoes, midges, etc. ( Family Chaoboridae - phantom midges Chaoborus sp. Family Culicidae - mosquitoes Culex sp. Aedes sp. Anopheles sp.- ~ Family Chironomidae - midges { Chironomus spp. (about 3 forms) Spaniotoma sp. a Cricotopus spp. (about 2 forms) ( unidentified chironomids (several forms) Family Ceratopogonidae - biting midges unidentified ceratopogonid Family Empididae - dance flies Hemerodromia sp. Class Arachnida - spiders, etc. (young, adults) Order Hydracarina - water mites unidentified mites (about 12 spp.) ~ [ =>

4 51 AD 3 (number /100 m ) of drif ting Table 16. Summary of overall catches / effort benthonic animals in 0.505 mm mesh plankton net tows in Mississippi River Station V-A (about proposed River Bend intake) and lower Bayou Sara, 1974 - 1975. (Numbers in larger type are sums of the underlying ordinal entries.) Bayou V-A 'V-A Sara TAXA 1974 1975 1975 ~ COELENTERATA - hydroid fragments 63.70 70.62 2,76 ENTOPROCTA "bryozoan" fragments 0.44 1.60 0.31 NEMATA - nematodes 0.15 '0.35 ANNELIDA - segmented worms 011gochaeta - oligochaetes 3.49 20.23 7.26 Hirudinca - leeches 0.05 MOLLUSCA - mollusks ~ Castropoda - snails 0.05 1.33 Pelecypoda - clams 0.49 0.56 OSTRACODA - seed shrimps 0.13 BRANCHIURA - fish lice 0.72 0.35 2.76 ISOPODA - aquatic sowbugs 0.98 1.32 1.84 AMPHIPODA - scuds 2.57 2.57 0.20 (] INSECTA - insects (larvae / adults) 144.79 95.02 74.43 Collembola - springtails 0.10 0.63 Ephemeroptera - mayflies 5.39 7.37 4.19 Odonata - dragonflies, damselflies 0.36 0.28 Hemiptera - bugs 1.26 1.04 17.48 Trichoptera - caddisflies 3.08 8.41 0.72 . Coleoptera - beetles 0.85 1.11 2.86 I ~ Diptera - mosquitoes, midges, etc.. 133.86 71.94 55.52 HYDRACARINA - water mites 2.31 2.29 5.01 3 MEAN TOTAL DRIFT /100 M 219.94 195.04 100.91 DRIFT MINUS SESSILE COLONY FRAQiENTS (Coelentera and Entoprocta) 155.47 122.82 97.84 NUMBER OF TAXA (RANGE) 8-28 11-22 5-20 15.8 15.7 10.8 NUMBER OF TAXA (MEAN)3) MEAN SAMPLE VOLUME (M 84.7 84.6 88.9 i em h09 v =

) 52 I Table 17 hat.er s /10N of truly planktonic animale is 0.505 mm mesh plankta, met towe in Mississippi River station V-A (above proposed River Bend intake) and lower Bayou Sara, 1974 - 1975. ( M=mid; E=early; L*1at e; EI=no ef f or t). E-AFE. L-API. I-WA T. L 8 TAT. F-ft"6. L-Jeg. E-Jt'1,, L y%, 3 -as10, 4 5FFT. MM, Eing, p-tyc, P-J AM. E-FFB. L-FEB. E-MAR .u{_ River (V-A). 1974 KE 2097 1740 1172 g155 12401 NE 8011 675 759 245a 279 179 1904 75 855 55 wt CLADOCERA - water fleae River (V-A). 197 5 201 327 NE 569 6670 2604 3011 1069 2477 2089 150 75 43 143 110 ut 102 246 Bayou Sara.1975 EE El NE 16262 1097063 7079 1636 75206 26337 61C1 17 31 6 62 NE ME NE sg Bioer (V-A),1974 EE 816 449 998 776 2523 NE 6434 1687 1915 855 739 1140 361 110 797 83 st COFEPODA - corepods River (V-A).197 5 275 585 NE 610 1771 554 605 749 533 1702 460 522 754 441 168 BE $47 2596 Bayou Sara.1975 EE EE NE 2007 87357 766 278 716 296 311 8 1 11 11 EE gE 3E gg MYS! TACE 4 - cpossue shrimpa EE 4 3 9 5 26 6 4 EE River (V-A).1974 NE 1 1 1 3 4 EE EE River (V-A),1975 EE EE sg 31 Rayou sara, 1975 WE NE ME E14APCA - shrisps, etc. NE 6 38 67 31 44 401 141 1 32 River (V-A).1974 51 13 70 39 96 57 37 mE NE B1ver D-A).1975 1 4 1 3 Et EE pt yg Bayou Sara.1975 NE EE NE River (V-A),1974 NE 2 19 11 EE 29 10 16 30 17 31 5 4 20 yE e 21PTERA PUPAE - sidEes, etc. River (V-A),1975 3 1 gg 6 12 9 16 15 16 9 4 17 12 11 NE 1 Bayou Sara,1975 EE WE ME 1 7 2 3 5 1 1 2 BE WE EI EE OSTEICICFYES - fish larvae & esas 3 39 ME 55 47 11 76 69 26 17 1 mr River (V-A).1974 EE 12 a 11 45 58 82 40 49 25 71 4 52 gg Elver (V-A),1975 151 44 4 20 469 415 81 5 3 2 NE DE ut ut Bayou Sara 1975 N1 KZ EE River (V-A),1974 EE 2314 2388 2170 1956 14g74 ug

1453, 2457 2770 3459 1152 1905 2429 191 1677 142 WE TCTAL E1*FIANET05 River (V-A),1975 479 913 st 1179 8'51 3178 3637 1858 3097 3960 719 713 900 744 293 m2 650 2842 3ayou Sara 1975 NE WE EE 18270 11'W8 7951 1921 76327 27106 6828 107 37 25 77 EE EE mz al O

O e

Tashle 18. Numbers /100 m3 of dr:"it: int benthenic animals in 0.. " =. =sas net tows in M12ssisst::::1 River Station Y-A (above pr-- r: seer.

==r e__~

intake) and Jamr Ba mn Sara, 1974 - 1975 Ot=sid ; D==aan_- -=- NE=no effort). M-JAN. E-FFB. 1.-FEE. -.*T -_2 m,

Li COCHAITA - worms E. Art. E **AT l M

-II N. L-JIN - I- ~~- E-JI'l

I~-

L'# River (V-A),1974 NE 3 2 Elver (V-A),1975 60 40 NE _~. Eayou Sara, 1975 NE NE NE EI O 9 ^0 1 2 d 7 17 4 5 NLMSCA - sr.sils ard class. 2 6 5 E River (V-A),1974 NE River (V-A),1975 f Eayou Sara, 1975 NE NE NE 81 2 NE i + CCIOTACIA - crustaceans NI { Elver (V-A),1974 NE 2 2 L L River (V-A),1975 2 NE, l Eayou Sara, 1975 NE NE NE NE 15 11 3 6 8 9 6 9 7 1 1 I

MI'UA - insects (larvae /ac. ults) 3 2

2 3 14 9 E Elver (Y-A), 1974 NE 59 29 L L I River (V-A),1975 98 23 NE ~ Eayou Sara, 1975 NE NE NE EI 122 408 ' 2~ 47 '3b ~~ ~33 . ',,I 23 28 45 .237 92 225 er 3c' D ACARINA - water mites 19 65 .45 56 i 19 t1 El River (V-A), 1974 NE 1 Elver (V-A), 1975 3 NE y Eayou Sara, 1975 . NE NE NE II 3 5 2 2 3 1 T;!;a:. CRIFT 21 12 1 River (V-A), 1974 NE 71 37 s* Elver (V-A),1975 177 68 NE

r..

~~ NE 428 560 MO 626 454 5;; 114 Eayou Sara, 1975 NE NE NE ~~ 54 93 117 4 08 148 1-284 11-435 2117 MISTS SESSIEE COI.CNY 77.ACMC-~; 33 76 84 _156 76 29 E l River (V-A),1974 NE 71 34 Elver (V-A),1975 163 64 NE Eayou Sara, 1975 NE NE NE ' JL 3'b' 5 426 24 49 598 NE 149 361 l 93 228 3'$ 45 54 59 32 76 84 .49 75 25 Nil g

Mollusks taken in Bayc _ Sara rre all snails whereas those um :.

a primarily young class. I O O O

~ 54 3 19. Numbers /100 m of planktonic animals in 0.505 mm resh plankton () Table net tows at stations across Mississippi River Transect V over 24-hour period, 27-28 August 1974. TIME Day Night Night Night Day Day Day 1700-2020-2330-0445-0705-1145-1610-1730 2045 2400 0515 0735 1215 1640 CLADOCERA East Bank (V-A) 1723 2403 2595 2119 1185 1312 1463 Midstream (V-c) 930 2608 2594 2586 1160 949 1540 West Bank (V-E) 145 996 1209 1767 117 102 125 COPEPODA East Bank (V-A) 166 202 361 242 141 106 160 Midstream (V-C) 66 185 245 247 119 80 177 West Bank (V-E) 5 77 158 174 14 6 7 OPOSSUM SHRIMP (MYSIDACEA) e East Bank (V-A) 1 2 1 Midstream (V-C) 2 2 1 West Bank (V-E) RIVER SHRIMP LARVAE East Bank (V-A) 66 63 84 84 91 52 86 Midstream (V-C) 10 20 33 36 30 32 32 ~ West Bank (V-E) 2 1 1 2 4 7 DIPTERA PUPAE (Mainly Chaoborus) East Bank (V-A) 17 30 53 50 21 7 9 Midstream (V-C) 8 20 44 89 33 13 13 West Bank (V-E) 45 60 111 FISH LARVAE & EGGS East Bank (V-A) 23 21 32 14 40 16 22 Midstream (V-C) 8 2 6 14 6 8 11 West Bank (V-E) 2 10 31 29 25 2 5 TOTAL PLANKTON East Bank (V-A) 1995 2719' 3126 2511 1479 1493 1740 Midstream (V-C) 1054 2837 2924 2972 1349 1082 1773 West Bank (V-E) 154 1129 1459 2083 156 114 144 NUMBER OF TAXA East Bank (V-A) 20 21 23 19 19 18 19 Midstream (V-C) 15 16 22 19 18 17 18 West Bank (V-E) 10 16 19 20 11 9 11 O

55 3 Tabla 20. Numbers /100 m of drif ting benthonic animals /in 0.505 ans mesh j plankton met tows at stations across Mississippi River Transect V over 24-hour period, 27-28 August 1974 f. 1 TIME Lty Night Night Night Day Day Day 1700-2020-2330-0445-0705-1145-1610-1 1730 2045 2400 0515 0735 1215 1640 i ~ SESSILE COLONY FRAGMENTS (hydroids and bryoroans) East Bank (V-A) 65 53 67 80 84 64 70 ~ l Midstream (V-C) 55 100 92 118 166 72 167 West Bank (V-E) 9 24 14 47 27 14 16 l MAYFLIES (EPl!EMER0PTERA) r East Bank (V-A) 11 29 14 10 5 4 2 i Midstress (V-C) 3 5 7 14 4 3 4 West Bank (V-E)* 7 4 3 4 1 CADDISFLIES (TRICH 0r ERA) ] East Bank (V-A) <1 / 3 4 7 e4 1 ~ Midstream (V-C) 3 4 4 6 5 3 4 2 6 3 1 2 West Bank (V-E) DIPTERA 1ARVAE (Mainly Chaoborus) East Bank (V-A) 40 62 68 39 15 41 67 Midstream (V-C) 51 53 78 54 40 60 85 West Bank (V-E) 10 78 61 46 10 8 15 ) OTHER DRIFT (Mainly clams, amphipods, dragonflies) East Bank (V-A! 2 5 6 7 2 4 2 1 Midstream (V-C) 6 7 12 12 9 10 15 2 4 4 6 2 2 2 West Bank (V-E) i TOTAL DRIFT East Bank (V-A) 119 153 159 143 130 114 141 Midstream (V-C) 118 169 193 204 224 148 275 ~ West Bank (V-E) 32 115 89 115 43 26 35 DRIFT MD:US SESSILE FORMS East Bank (V-A) 53 100 92 63 46 50 71 i Midstream (V-C) 63 69 101 86 58 ~ 76 108 l West Bank (V-E) 23 91 75 68 16 12.. 19 NLMBER OF TAXA East Bank (V-A) 11 14 13 14 11 9 8 8 I4 11 13 11 9 12 Midstream (V-C) "~ West Bank (V-E) 5 10 11 13 8 10 5 ~

Mayfly nymphs taken at West Bank were mainly Heptagen11ds (Stenonema, etc.),

whereas the ottiers were mainly Ephemerida (Tortopus, etc.). I O .y.m. _ _. _ _ ~,,, _ -. -. _ _ _.. __+my .~. _y, _,

56 ) BENTH0S Mississippi River Petersen grab data for the seven quarterly sampling periods at River j 4-stations are presented in Tables 21 - 27. ' Temporal patterns of relative. abundance of the major groups were similar for the two years with the { exception of mayfly larvae, which in summer,1975, were roughly seven times as numcrous as they had been in the previous. summer. This marked difference in mayfly densities may be related at least in part to increased stability in clay substrates, especially along east bank stations (V-A, IV-A, III-A) in 1975 as compared to 1974 (see below). General structure of benthic communities at Mississippi River stations is summarized for 1974-75 in Table 28, which may be compared with Figure E-27. of' the River Bend Environmental Report (although the latter does ~ not present as much detail). Dominant groups at west shore stations on the upper two transects (V-E, IV-E) have changed somewhat since the initial phase of sampling in 1972-73. Whereas burrowing mayfly. larvae and Asiatic class used to be (1972-73) the dominant benthic invertebrates at V-E they now rank behind midge larvae and oligochaete worms. At IV-E burrowing mayflies seem to have replaced oligochaetes as the most numerous animals. These observations may merely reflect the decreased frequency of. sampling in 1974-75, but there has been a' definite shift in substrate type at upper west shore stations - from fine sand and mud to coarser materials - since the 1973 flood. A comparison of overall densities of benthic invertebrates at river _() stations between the initial intensive sampling phase of 1972-73 and the ~ S

57 i ) quarter 1y interim monitoring pr.ogram of 1974-75 is given in Table 29. With the exception of Station V-E all shoreline stations seem to have unde,rgone ~ a marked decline in relative sbundance cf benthic invertebrates. Again, the differences may in part reflect the change from a monthly to a quarterly sampling frequency, but they probably have more to do with a temporary decline in stability of shoreline substrates. In general, the first three quarters of the present study (Spring-Fall,1974) represent a !' bad" year in the aftermath of the record flood, with bank eloughing along the east shore and deposition along the west shore almost as extensive as ;in the latter - half of 1973. By 1975 shoreline substrates seem to have become more stable. albeit in slightly different local patterns (see above). If only 1975 ' " ' data are compared with those of the earlier sampling phase the differences ) are not so pronounced. Alligator Bayou Ekman grab data for the seven quarterly sampling periods at Alligator 1 ~ Bayou stations are presented in Tables 30-36. 011gochaete worms (mostly Tubificidae) and dipteran larvae (most1p midges, Chironomidae) dominated most samples from all stations as noted in earlier reports. Densities of benthic invertebrates at Stations 1 and 4 generally followed the patterns noted in earlier reports, with maxima in the spring and summer and minima 'in the fall and winter. Station 3 (" Grassy Lake") data shows the reverse, I at least for fall-winter, 1974-75, with peak densities of oligochaetes obtaining in those quarterly periods. But the fall, 1975, oligochaete ~ densities were not noticeably high. General benthic community structure at Alligator Bayou stations, as r-} v indicated by Ekman grabs for the seven quarterly sampling periods, is e

58 depicted in Table 37. As noted above, the dominant, groups remained the D same as described in earlier reports, although station 3 (." Grassy Lake") exhibited a somewhat greater diversity in 1974-75 than it had in earlier phases of work at River Bend. This increased' diversity probably reflects the greater stability of water levels in " Grassy Lake" during the last two years, due to the impounding activity of beavers. Table 38 compares the mean densities of benthic invertebrates at Alligator Bayou stations for four seasons during tM raeant monitoring and the initial intensive phase of sampling (data for the latter compiled ~ from Tabic 33 of the First Cumulative Summary). With exception of fall and winter, 1974-75, densities in " Grassy Lake" (attributable to the abundance peaks of oligochaetes discussed above), the temporal and spatial trends exhibited by the two sampling phases show general agreement. Grants Bayou Seasonal patterns of relative abundance of benthic invertebrates at the two Grants Bayou stations are depicted in Tables 31 - 36. Greatest densities were observed in the colder months (February and November, 1975) when midge larvae and midge larvae and oligochaetes, respectively, readhed abundance peaks. General community structure at the two stations is reflected by Table 37. As noted in earlier reports midge larvae tend to I dominate the benthos of Grants Bayou. Oligochaetes tend to become numerically important - yet still not more a' undant than midges - mainly during times b of intermittent flow (e.g. summer 1974, and fall 1975). This point is emphasized by the absence of oligochaetes from Summer 1975 samples (Table 35), j _ for this was the first summer among the four years of sampling experience t at River Bend during which Grants Bayou maintained at least some flow. ~

59 [a) Tabic 21. Mean number of specimens /8 in triplicate Petersen grabs at Mississippi River Stations,17 April 1974 (Spring Quarterly). ~ V-A V-C V-E IV-A IV-C IV-E III-A III-C III-E PORIFEP.A 4 COELENTERATA 4 NEMATODA 4 BRYOZOA 4 Entoprocta Ectoprocta ANNELIDA Oligochaeta 4 22 7 4 32 176 11-111rudinea CRUSTACEA Isopoda 4 36 ) Amphipoda IlYDRACARINA INSECTA Collembola 4 4 Piccoptera Ephemeroptern Ephemeridae 4 7 161 266 (. IIeptageniidae 4 4 18 4 Odonata l Tricinoptera liydropsychidae 4 .,. 4 Psychomylidae Diptera Culicidae Chaoboridae 4 4 Chironomidae 25 4 4 14 4 4 Ceratopogonidae g 4 Tabanidae 4 Anthomyiidae MOLLUSCA Castropoda 11 7 4 7 Pelecypoda 4 12 '86 15 22 292 4 461 ' TOTAL. O l

60 t D 2 in triplicate Petersen grabs at Tabic 22. Mean number of specimens /m ' Mississippi River Stations,19 August 1974 (Summer Quarterly). V-A V-C V-E IV-A 'IV-C IV-E III-A III-C III-E i PORIFERA 7 COELENTERATA NEMATODA BRYOZOA Entoprocta Ectoprocta ANNELIDA 011gochaeta 4 7 136 212 4 / Ilirudinea CRUSTACEA 7 Isopoda 7 Amphipoda 1) IIYDRACARINA INSECTA 4 Collembola Plecoptera Ephemeroptera Ephemeridae 68 11 4 18 93 25 I 4 Heptageniidae Odonata ~ - Trichoptera Hydropsychidae , 7 Psychomyiidae ~ Diptera Culicidae Chaoboridae Chironomidae 25 18 36 4 7 7 Ceratopogonidae 4 4. ~ l-4 Tabanidae Anthomyiidae HOLLUSCA Castropoda Felecypoda 111 11 4 . TOTAL, 104 133 36 11 30 32 251 4 248 O S

61 2 Table 23.

Hean number of specimens /m in triplicate Petersen grabs at

~ '- Mississippi River Stations, 14 November 1974 (Autumn Quarterly). ~ '~ ~ V-A V-C' V-E IV-A IV-C IV-E III-A III-C III-E PORIFERA COELENTERATA ~ NEMATODA BRYOZOA Entcprocta Ectoprocta ANNELIDA 011gochaeta 65 22 86 456 176 Hirudinea CRUSTACEA Isopoda Amphipoda -11 4 Os HYDRACARINA ~ INSECTA ~ Collembola Plecoptera Ephemeroptera ~ Ephemeridae 39 22 7 .65 Heptageniidae 4 4 Odonata ~ Trichoptera Hydropsychidae n.

n. u - : e., -

Psychomyiidae Diptera Culicidae ? Chaoboridae 4 Chironomidae 7 7 7 7 I 7 Ceratopogonidae ..r.,..u.ei. g Tabanidae' Anthomyiidae ~ MOLIUSCA Castropoda Pelecypoda 25 7 11 11 29 TOTAL, 147 7 55 97 22 539 11 205 A -() G e eu "

1 62 2 in triplicate Petersen grabs at - Table 24. Mean number of specimens /m Mississippi River Stations, 7 February 1975 (Winter Quarterly). f V-A V-C V-E IV-A IV-C IV-E III-A III-C III-E PORIFERA COELENTERATA 4 NEMATODA BRYOZOA Entoprocta Ectoprocta 11 ANNELIDA 18 11 18 12/4 43 011gochaeta e Hirudinea ~ CRUSTACEA Isopoda 4 Amphipoda HYDRACARINA INSECTA ,Collembola Plecoptera Ephemeroptera 11 Ephemeridae I Heptageniidae 4 Odonata 4* Trichoptera Hydropsychidae Psychomyiidae Diptera Culicid se Chaoboridae 7 4 Chironomidae 14 83 57

68 11 4

Ceratopogonidae 7 4 11 11 11 f. Tabanidae Anthomyiidae HOLLUSCA Castropoda 68 Pelecypoda 21 4 127 79 112 1296 123 ~ TOTAL. e,,_

63 f ~ Table 25. Mean number of specimens /m2 in triplicate Petersen grabs at - ' Mississippi River Stations, 6 May 1975 (Spring Quarterly). '~ ~ l ^ V-A V-C V-E IV-A IV-C IV-E III-A III-C III-E PORIFERA COELENTERATA NEMATODA 4 BRYOZOA Entoprocta Ectoprocta ANNELIDA ~~ Oligochaeta 4 14 4 54 922 Ilirudinea CRUSTACEA Isopoda 4 4 ( Amphipoda 4 HYDRACARINA INSECTA 4 Collembola Plecoptera Ephemeroptera Ephemeridae 65 7 47 4 4 Heptageniidae Odonata Trichoptera Hydropsychidae Psychomyiidae Diptera Culicidae Chaoboridae Chironomidae 4 Ceratopogonidae 14 i 7. 7 .s, Tabanidae 2 Anthomyiidae MOLLUSCA l Castropoda Pelecypoda 4 4 TOTAL. 73 22-8 28 11 55 58 4 926 6V 4 e

64 ~ Mean number of specimens /m2 in triplicate Petersen grabs at '" ~* Table 26. Mississippi River Stations,18 August 1975 (Summer Quarterly). V-A V-C V-E' IV-A IV-C IV-E III-A III-C III-E PORIFERA ~ COELENTERATA NEMATODA BRYOZOA Entoprocta Ectoprocta ANNELIDA 011gochaeta 7 32 4 43 531 Ilirudinea CRUSTACEA Isopt.la Amphipoda 29 _ O HYDRACARINA INSECTA Collembola Plecoptera ,;r Ephemeroptera Ephemeridae 197 4 405 4 718 108 Heptageniidae l Odonata Trichoptera Hydropsychidae ,,n. n Psychomylidae i,_ Diptera Culicidae 4 4 Chaoboridae 4 Chironomidae 11 4 11 4 11 7 .4 4 Ceratopogonidae Tabanidae Anthomylidae HOLLUSCA Castropoda 4 4 Pelecypoda 7 4 .4 18 TOTAL, 263 11 4 441 11 16 765 8 672 .Ilme [ e

a

65 _O ~ . Table 27. Mean number of specimens /r2 in triplicate Petersen grabs at Mississippi River Stations,31 October 1975 (Autumn Quarterly). i. -~ i V-A V-C V-E IV-A IV-C IV-E III-A -III-C III-E PORIFERA COELENTERATA NEMATODA BRYOZOA Entoprocta Ectoprocta ANNELIDA 011gochaeta 14 40 69 4 18 158 4 402 Hirudinea CRUSTACEA Isopoda ~h Amphipoda v HYDRACARINA INSECTA Collembola Plecoptera Ephemeroptera Ephemeridae 7 59 7 4 223 25 g Heptageniidae 7 Odonata ~

Trichoptera Hydropsychidae Psychomyiidae Diptera Culicidae Chaoboridae 4

Chironomidae 43 86 4 4 115 7 29 ~ Ceratopogonidae 4 4 7 Tabanidae Anthomyiidae MOLLUSCA Gastropoda Pelecypoda 7 11 7 32 36 50 TOTAL, 75 4 196 87 44 360 201 11 513 O AJ G 6

66 e Table 28. Community structure of benthic invertebrates at Mississippi River b) Stations, 1974 - 1975, as reflected by.ranki.ng of most frequently-occurring groups in descending order of relative abundance (speci-2 mens /m ) in Petersen grabs. HIDSTREAM WEST BANK EAST BANK (Station A) (Station C)

(Station E)

TRANSECT V burrowing mayfly larvae Asiatic clams midge larvae midge larvae . biting midge larvae oligochaetes oligochaetes burrowing mayfly amphipods larvae Asiatic clams Asiatic clams biting midge larvae biting midge larvae nematodes phantom midge larvae TRANSECT IV - () burrowing mayfly larvae Asiatic clams burrowing mayfl.ies oligochactes biting midge larvae midge larvae midge larvae oligochaetes biting midge larvae biting midge larvae I TRANSECT III oligochaetes Asiatic clams oligochaetes burrowing mayfly larvae biting midge larvae burrowing mayfly Asiatic clams larvae midge larvac Asiatic clams heptageniid mayfly larvac midge larvae-dragonfly larvae i anumme W A -q ;

67 2 Table 29. Comparison of mean densities (specimens /m ) of benthic invertebrates in Petersen grab samples at Mississippi River Stations, 1974-75 versus 1972-73.* EAST BANK MIDSTREAM WEST BANK (Station A) (Station C) '(Station E) ' TRANSECT V 1974-75 98 28 73 1972-73 1064 11 74 9 TRANSECT-IV 1974-75 108 14 88 1972-73 428 8 515 TRANSECT III~ 1974-75 486 6 450 1972-73 1151 6 2914 ~ l

Note that 1972-73 data were. collected by single grabs per station on a monthly basis whereas 1974-75 data were collected by triplicate grabs per station only a quarterly basis.

t I W w _l__.__-_______-._

6s Table 30. Mean number of specimens /m2 in triplica,e Ekman grabs at Alligator t -(} and Grants Bayou Stations, 6 May 1974 (Spring Quarterly). j ALLIGATOR BAYOU GRANTS BAYOU l' 3 '4' 1 2 PORIFERA - sponges (no effort) (no effort) i' ~ COELENTERATA - hydroids (no effort) (no effort) I t NEMATA - nematodes j4 ANNELIDA 011gochaeta - aquatic earthworms 438 2985 i Hirudinea - leeches 14 i CRUSTACEA i Isopoda - aquatic sowbugs 29 1-Amphipoda - scuds 79 ~( ) Decapoda Palaemonidae - shrimps 14 i Astacidae - crayfishes HYDRACARINA - water mites ( ~ INSECTA Ephemeroptera - mayflies Odonata - dragonflies t } Hemiptera - bugs l l Trichoptera - caddisflies ~ l Coleoptera - beetics 7 l Diptera - true flies 157 114 HOLLUSCA Castropoda - snails 86 14 3 l -w Pelecypoda - clams 50 TOTALS 846 3141 1 e n

69 Mean number of specimens /m2 in triplicate 3Ekman grabs at'A111 gator Table 31. and Grants Bayou Stations, August 1574 (Summer Quarterly). ' ALLIGATOR BAYOU CRANTS BAYOU 1 3 '4 1 2 PORIFERA - sponges ~ . COELENTERATA - hydroids NEMATA - nematodes } ANNELIDA 86 1952 1235 57 115 011gochaeta - aquatic carthworms Hirudinca - leeches . CRUSTACEA 14 Isopoda - aquatic sowbugs / Amphipoda - scuds Decapoda 14 14 ' Palaemonidae - shrimps 29 Astacidae - crayfishes HYDRACARINA - water mites '~ INSECTA Ephemeroptera - mayflies 216 28 Odonata - dr'agonflies 14 Hemiptera - bugs i Trichoptera - caddisflies '~ Coleoptera - beetles Diptera - true flies 588 215 129 215 144-HOLLUSCA Gastropoda - snails 14 14 Pelecypoda - clams 14 57 57 14 14 716 2252 1637 357 287 TOTALS I

70 Table 32. Mean number of specimens /m2 and Grants Bayou Stations, November 1974 (Autumn Qu (a i ' ALLIGATOR BAYOU _ GRANTS BAYOU 1 3 4-1 2 ~ PORIFERA - sponges COELENTERATA - hydroids 14 NEMATA - nematodes 14 57 ANNELIDA 011gochaeta - aquatic eartftworms 57 15830 330 57 Ilirudinea - Iceches CRUSTACEA Isopoda - aquatic sowbugs 29 14 14 Amphipoda - scuds / 28 Decapoda ,() Palaemonidae - shrimps Astacidae - crayfishes 14 14 IIYDRACARINA - water mites INSECTA i Ephemeroptera - mayflies 28 57 14 Odonata - dragonflies IIemiptera - bugs 14 Trichoptera - caddisflies 14 Coleoptera - beetles I Diptera - true flies 43 2081 72 14 201 HOLLUSCA Castropoda - snails 14 14 ~'/ ^;. Pelecypoda - clams a 14 e TOTALS 185 18081 458 14 314

71 Table 33, Mean number of specimens /m2 in triplicate Ekman grabs at Alligator and Grants Bayou Stations, January - February 1975 (Winter Quarterly). 0 ' ALLIGATOR BAYdU GRANTS BAYOU 1 3 4 1 2 14 PORIFERA - sponges COELENTERATA - hydroids r NEMATA - nematodes ANNELIDA 011gochaeta - aquatic cartfworms 14 8855 57 28 14 Hirudinca - leeches CRUST CEA 14 Isopoda - aquatic sowbugs / Amphipoda - scuds ~ Decapoda ) Palaemonidae - shrimps Astacidae - crayfishes HYDRACARINA - vater mites t ~ INSECTA Ephemeroptera - mayflies 29 57 14. 14 Odonata - dragonflies Hemiptera - bugs Trichoptera - caddisflies ~ Coleoptera - beetics' Diptera - true flies 57 374 2394 1320 HOLLUSCA Gastropoda -- snails 129 Pelecypoda - clams 85 TOTALS 71 9486 114 2450 1348 ~ N

72 2 in triplicate Ekman, grabs at Alligator Mean number of specimens /m Tabic 34. and Grants Bayou Stations, May 1975 (Spring Quarterly). 'ALLICATOR BAYOU CRANTS BAYOU 1 ~3

- 4' 1

2 PORIFERA - sponges ~ COELENTERATA - hydroids 14 NEMATA - nematodes -~ j ANNELIDA I 011gochaeta - aquatic cartfiworms 4234 2555 430 28 14 .i I Hirudinea - leeches i i CRUSTACEA c) 101 14 Isopoda - aquatic sowbugs 14 Amphipoda - scuds Decapoda Palaemonidae - shrimps Astacidae - crayfishes 14 HYDRACARINA - water mites INSECTA 14 14 Ephemeroptera - mayflies 14 Odonata - dragonflies 4 Hemiptera - bugs i 14 Trichoptera - caddisflies f Coleoptera - beetles 674 201. 330 Diptera - true flies HOLLUSCA Gastropoda - snails 57 14 14 Pelecypoda - clams '~ 4965 2583 573 257 386 ~ TOTALS

+--6 _.,. ~ 2 A _.m 73 Table 35. Mean number of specimens /m2 in triplicate Ekman grabs at Alligator and Grants Bayou Stations, July - August 1975 (Summer Quarterly). v() d ' ALLIGATOR BAYOU GRANTS BAYOU 'l' 3 4-1 2 PORIFERA - sponges COELENTERATA - hydroids NEMATA - nematodes ANNELlDA l {~ Oligochaeta - aquatic eartf. worms 2460 144 i Hirudinea - Iceches CRUSTACEA Isopoda - aquatic sowbugs 43 72 Amphipoda - scuds 14

114, Decapoda

. O Palsemonidae - shrimps 29 Astacidae - crayfishes HYDRACARINA - water mites ( i INSECTA Ephemeroptera - mayflies 14 100 28 Odonata - dragonflies 14 14 Hemiptera - bugs ~ Trichoptera - caddisflies 14 g Coleoptera - beetles 14 Diptera - true flies 215 502 186 144 172 ~ MOLLUSCA Gastropoda - snails 215 28 i -[) \\ Pelecypoda - clams 474 29 TOTALS 215 3779 687 158 200 l l 1.

74 ~ 2 in triplicate Ekman grabs at Alligator Table 36. Mean number of specimens /m _() and Grants Bayou Stations, October - November 1975 (Autumn Quarterly). $ ALLIGATOR BAYOU GRANTS BAYOU r 1 3 ~4 1 2 ) \\ \\ PORIFERA - sponges ~ COELENTERATA - hydroids l l i 14 I NEMATA - nematodes ANNELIDA 28 2512 388 1320 315 ~ 011gochaeta - aquatic carthworms Birudinea - leeches CRUSTACf-57 ,14 14 43. ~ Isopoda - aquatic sowbugs f 144 Amphipoda - scuds s Decapoda Palaemonidae - shrimps Astacidae - crayfishes ~ HYDRACARINA - water mites INSECTA Ephemeroptera - mayflies 14 129 29 14 Odonata - dragonflies Hemiptera - bugs I Trichoptera - caddisflies C'oleoptera - beetles Diptera - true flies 227 373 746 6114 2066 MOLLUSCA 115 373 14 Castropoda - snails _{} 445 43 Pelecypoda - clams 269 3530 1837 7491 2424 TOTALS l

75 ( Table 37. Community structure of benthic invertebrates at Alligator and Grants Bayou Stations, 1974 - 1975, as reficcted by ranking of most frequently-occurring groups in descending order of relative abundance (specimens /m2) in Ekman. grabs. ALLICAT0R BAY 0U l ' Station 1 Station 3 Station 4 oligochactes oligochaetes oligochaetes dipteran larvac dipteran larvae dipteran larvae '~ (mainly midges) (mainly midges) (mainly midges) snails fingernail clams mayfly larvae isopods snails snails fingernail clams isopods amphipods mayfly larvae mayfly larvae isopods nematodes fingernail clams grass shrimp amphipods dragonfly larvae GRANTS BAY 0U I Station 1 Station' 2 dipteran larvae dipteran larvae (mainly midges) (mainly midges) oligochaetes oligochaetes mayfly larvae mayfly larvae isopods dragonfly larvae snails caddisfly larvae I 4 m l.

t 76 6 Table 38. Comparison of mean densities (specimens /m2) of benthic invertebrates in triplicate Ekman grabs by' seasons at Alligator Bayou Stations, j 1974-75 versus 1972-73.* i ( Station 4 ~ Station 1 Station 3-1974-75 1972-73 1974-75 1972-73 '1974-75 1972-73 I ~ f Summer 716 8195 2252 2823 1637 662 Fall 185 597 18081 f.463 72 307 Winter 71 835 9486 1983 114 606-Spring 4965 10359 2583 1577 573 576 ~

Note that 1972-73 data were collected on a monthly basis whereas 1974-75' data were collected only on a quarterly basis.

(:3) t w t w H* i ~ f w O t h = 1

77 _ ) FISHES A taxonomic list of the fishes collected by various. gears in three environments of the River Bend study arca~during the 1974-75 interim monitoring program is presented in Table 39. Sixty-eight species were recorded, indluding three previously unknown from the study area 'the t least killifish (Heterandria formosa); the Gulf pipefish (Syngnathus scovelli); and the striped bass (Morone saxatilis). Of the three only the least killifish was unexpected, and our collection of a singic specimen by dipnet appears ~~ to constitute a slight upstream extension of the known range along the main-stem Mississippi. These additions bring to 87 the total number of fish species whose occurrence has been documented in the River Bend study area (i.e., river ,OG between miles 266 and 256, Alligator Bayou on and immediately below GSU property, and Grants Bayou below La. Highway 61) in four years of sampling. Eighty have b'een taken in the river (including about 20 displaced forms from preferred habitats elsewhere); 65 from Alligator Bayou (including about 24 nonresidents); and 21 from Grants Bayou (including about 5 nonresidents). Mississippi River Catch per effort data for three gears at Mississippi River stations is summarized in Tables 40-43. Small fishes (seine data, Table 40) exhibited t the greatest diversity and relative abundance during spring and summer quarterlies. ~ Despite minor shifts in rankings, attributable perhaps to a decreased sampling frequency, the same species tended to dominate catches during this interim monitoring phase as had led in relative abundance during the 1972-73 period. 3) Skipjack herring, gizzard shad, blacktail shiners, mimic shiners, and blue 4

I 78 _{} catfich (young) showed slight declines in relative abundance as compared with earlier sampling, whereas threadfin shad, silvery minnows, river carpsuckers, and Mississippi silversides were slightly more abundant. Fever species and individuals of displaced swamp and tributary fishes were encountered during 1974-75 as compared with the earlier sampling phase that encompassed the 1973 flood. f Trammel-netting yielded a greater variety of fishes.but generally lower catches / effort in 1974-75 as compared to earlier sampling phases. Among the major species there were few, if any, substantive changes in ~ rankings on the basis of relative abundance, but bowfin, gizzard shad, blue catfish, flathead catfish, and freshwater drum were all roughly half to slightly less than half as abundant as they had been in 1972-73 sampling (see Table 22, Second Cumulative Summary). On the other hand, shovelnose -O sturgeon and bigmouth buffalo were caught in greater numbers and smallmouth buffalo appeared in about equal quantities as compared with 1972-73. catches for 1975 (especially the last three quarters) were somewhat higher than those for 1974, paralleling the pattern noted for river benthos that was attributed ~ to 1974 having been a " bad" year in the aftermath of'the record flood. Indeed, local commercial fishermen who were interviewed generally agreed that l m2 1974 was a poor year. A similar - although not so pronounced - difference in catches between the years was observed in hoopnets (Table 43). f Alligator Bayou ~ Catches / effort for quarterly periods at Alligator Bayou stations are presented in Tablec 44-46. These data are then used to derive the general community structures of fishes at the three stations (Table 47). b Most of the differences between the interim monitoring phase and the -sse earlier sampling phase are probably attributable to the reduced frequency of 9 w

79 collecting in 1974-75. Certain species (e..g. silvery minnow, blacktail shiner) {} ~ apparently migrate in and out of station areas in response to hydrographic changes and/or as a part of their normal life-history requirements. These species generally occur in high densities and, therefore, when encountered will often boost the overall catch / effort for that particular time. The , monthly sampling of the 1972-73 phace probably allowed a better understanding of the oscillating abundances of such species. Other forms which show similar patterns are the golden shiner, the pirate perch, and the several species which tended to appear as displaced individuals, either from the river or upland creeks and ponds, during flooding. More notable changes involve species which have been interpreted as fulltime i residents in Bayou habitats, especially those forms associated with rooted aquatic vegetation at Station 4. Grass pickerel, banded pygmy sunfish, bantam sunfish, slough darrers, and cypress darters were either absent or markedly less abundant in samples from 1974-75 whereas they had appeared to be important species in the earlier sampling phase. The dense mats of Nite 11a and Callitriche which had existed at Station 4 in 1972 were prevented from developing by the winter and spring flood inundations of 1972-73 and 1973-74. Absence or scarcity of the abovehmentioned species at Station 4-in 1974-75 is probably ~ i a direct result of the local absence of appropriate vegetation. Grants Bayou f Catches / effort at Grants Bay 6u stations are summarized in Table 48. When compared with the data gathered during the 1972-73 period the results of interim monitoring sampling show general agreement, although a greater diversity of fishes was observed in the former period. The reduced diversity _( is probably due in large part to incomplete recovery from the deleterious effects of sweet potato processing effluents that were released above the 5

= 80 study area in the Fall of 1973. During the period immediately following l these releases, which was. not encompassed by routine sampling other than the last fall' quarterly of the initial program, fishes were virtually l extirpated from our Grants Bayou stations. j - 1 ( 4 4 t I ~ 6 = I- ' O J

e 1

i I i = l l i I A e M' ~ f

-O

.l ~.__.__...._,._,_-.._,_.._______.____..-___.:_,_________,.__,._____________.,..._-__,_,__..__

81 ~() Table 39. Taxonomic list of fishes collected in three environments of River Bend study area, 1974-1975. (T= trammel nets; S= seines; E=electrofishing; D=dipnet.) Alligator Grants River Bayou Bayou Scaphirhynchus platorynchus (Rafinesque)-shovelnose sturgeon T Polyodon spathula (Walbaum)-paddlefish T Lepisosteus oculatus Winchell-spotted gar S-T S-E rL. osseus (Linnaeus)-longnose gar T !Amia calva Linnaeus-bowfin T E Alosa chrysochloris_ (Rafinesque)-skipjack herring S-T ~ Dorosoma cepedianum_ (Le Sucur)-gizzard shad S-T-H S-E S S D. potenense_ (Gunther)-threadfin shad Hiodon alosoides (Rafinesque)-goldeye S-T Esox americanus vermiculatus Le Sucur-grass pickerel S S Cyprinus carpio_Linnaeus-carp S-T-H S-E Hybognathus nuchalis Agassiz-silvery minnow S S Hybopsis aestivalis_ (Girard)-speckled chub S H. storeriana (Kirtland)-silver chub S S N'otemigonus crysoleucas (Mitchill)-golden shiner 'S S S Notropis atherinoides Rafinesque-emerald shiner S .S N blennius (Girard)-river shiner S S S /) N[. chrysocephalus (Rafinesque)-striped shiner (_/ N. fumers Evermann-ribbon shiner S ~ [.longirostris (Hay)-longnose shiner S S ((. lutrensis (Baird and Girard)-red shiner S N[. maculatus (Hay)-taillight shiner S S S NL. shumardi (Girard)-silverband shiner S g ((. texanus (Girard)-weed shiner N. venustus_ (Girard)-blacktail shiner S S S N volucellus_ (Cope)-mimic shiner S Opsopoeodus emiliae (Hay)-pugnose minnow S S Pimephales vigilax (Baird and Girard)-bullhead minnow S Semotilus atromaculatus (Mitchill)-creek chub S Carpiodes carpio (Rafinesque)-river carpsucker S-T-H S-E Erimyzon oblongus (Mitchill)-creek chubsucker S 'Ictiobus bubalus (Rafinesque)-smallmouth buffalo S-T-H S-E I. cyprinellus (Valenciennes)-bigmouth buffalo T S-E Minytrema melanops (Rafinesque)-spotted sucker E Ictalurus furcatus (Le Sucur)-blue catfish S-T I, melas (Rafinesque)-black bullhead T-H E S I. natalis (Le Sueur)-yellow bullhead H S-E S 1 punctatus (Rafinesque)-channel catfish S S Pylodictis olivaris (Rafinesquc)-flathead catfish T-H Aphredoderus sayanus (Gilliams)-pirate perch S S l Fundulus olivaceus (Storer)-blackspotted topminnow S S S Gambusia affinis (Baird and Cirard)-mosquitofish S S S I _[#) Heterandria formosa Agassiz-least killifish*t D l Labidesthes sicculus (Cope)-brook silverside S S i G

T:blo 39. C:ntinuzd. Alligator drants River Bayou Bayou (-] \\~j Menidia nudens Hay-Mississippi silverside S Syngnathus scovelli_(Evermann and Kendall)-Gulf pipefish

S Morone chrysops (Rafinesque)-white bass S-T-H M. saxatilis (Walbaum)-striped bass
T Centrarchus macropterus (Lacepede)-flier S-E Chaenobryttus gulosus (Cuvier)-warmouth S

S-E Elassoma zonatum Jordan-banded pygmy sunfish S Lepomig cyane11us_ Rafinesque-green sunfish S S S le humilis (Girard)-orangespotted sunfish S L. macrochirus Rafinesque-bluegill S S-E S S S Ig marginatus (Holbrook)-dollar sunfish 1.. megalotis (Rafi..esque)-longear sunfish S S-E S-E

1. microlophus (Gunther)-redear sunfish 1

S S-E e punctatus (Valenciennes)-spotted sunfish l

1. sy=metricus Forbes-bantam sunfish S

1Micropterus salmoides (Lacepede)-largemouth bass S-T S-E. S Pomoxis annularis Rafinesque-white crappie S-T-H S-E P. nigromaculatus (Le Sueur)-black crappie .S-T S-E Etheostoma asprigene (Forbes)-mud darter S / S E,. chlorosomum (Hay)-bluntnose darter D E. gracile (Girard)-slough dartert Stizostedion canadense (Smith)-sauger S Aplodinotus grunniens Rafinesque-freshwater drum S-T-H S-E I~ i Mugil cephalus Linnaeus-striped mullet S O'

Not recorded in previous reports.

tNot taken in routine sampling, found in dipnet collections from flooded I swamp area. e ene I we. Wue wl om

i 83 OTcbic 40. Catch / Effort (number per seine-hour) of fishes in seine collections at . Mississippi River Stations, 1974 - 1975. ~ Spring Summer Fall Winter Spring Summer Fall 1974 1974 1974 1975 1975 1975-1975 Mean Frequency dpotted gar 0.4 0.07 5 ekipjack herring 0.2 0.4 0.14 9 gizzard shad 2.4 5.8 0.6 5.2 3.29 41 threadfin shad 5.5 170.9 0.6 75.6 66.85 50 gnideye 0.5 0.14 5 grass pickerel 2.8 1.1 0.70 18 c:rp 3.3 .42 5 cilvery minnow 1.7 74.7 5.2 23.78 27 cpeckled chub 3.1 3.7 18.7 3.711 27 cilver chub 2.6 14.7 6.3 1.3 3.57 36 ~ golden shiner 0.2 0.07 5 emerald shiner 23.8 10.2 2.7 7.8 20.7 ' 11.3 13.71 82 river shiner 3.8 5.1 7.3 2.8 67.4 7.5 16.57 64 longnose shiner 6.7 0.4 0.21 9 r'7ed shiner 1.7 0.2 0.4 0.49 23 i_jaillight shiner 0.6 0.7 0.21 9 cilverband shiner 26.2 8.6 9.3 13.9 ' 5.9 16.3 12.66 59 blacktail shiner 30.3 0.9 0.7 33.3 0.4 1.3 7.34 50 mimic shiner 3.8 0.7 0.84 9 pugnose minnow 0.2 1.1 1.1 0.42 14 bullhead minnow 0.7 0.2 1.5 1.3 0.56 18 river carpsucker 32.3 2.0 0.6 52.2 19.86 41 smalLmouth buffalo 0.3 0.7 0.6 0.21 14 blue catfish 0.7 37.3 4.13 18 channel catfish 1.0 6.3 104.0 1.1 1.1 6.3 13.71 64 pirate perch 1.7 1.1 0.49 14 blackspotted topminnow 0.4 0.07 5 mosquitofish 9.3 1.4 6.7 9.3 1.3 4.97 50 brook silverside 0.5 0.14 5 Mississippi silverside 1.7 15.6 1.3 20.7 8.8 9.65 59 Gulf pipefish 0.2 0.7 0.14 9 white bass 3.0 0.4 0.98 9 warmouth 1.7 3.3 0.4 0.84 23 green sunrish 12.8 1.61 5 orangespotted sunfish 9.7 15.6 0.4 3.99 18 bluegill 7.6 0.2 40.0 1.1 6.85 41 Gollarsunfi'h s 1.4 1.2 0.28 9 longear sunfish 0.7 8.9 3.7 2.24 36

[ e 84 Table 40. Continued. Spring Summer Fall Winter Spring Summer Fall 1974 1974 1974 1975 1975~ ~1975' 1975' Mean Frequenc-spotted sunfish 1.7 0.21 9 bantam sunfish 0.6 0.07 5 largenouth bass 0.3 0.7 0.7 0.6 0.42 27 white crappic 0.7 0.7 1.7 1.1 0.77 27 black crappie 0.7 3.3 0.4 0.70 14 sauger 2.0 0.21 5 freshwater drum 1.6 1.3 0.4 0.70 18 striped mullet 0.5 0.14 5 Total 141.4 349.8 204.7 40.0 130.6 282.3 55.0 229.1 Effort 2.9 4.3 1.5 0.3 1.8 2.7 0.8 (seine-hours) (_s i t e e

85 Table 41. Catch / Effort (number per net-day) of fishes taken in trammel nets at Mississippi River Stations, 1974 - 1975. Spring Summer Fall Winter Spring Summer Fall 1974 1974 1974 1975 1975 1975 1975 Mean Frequency -. shovelnose sturgeon 0.08 0.11 0.56 0.22 0.12 57 paddlefish 0.11 0.01 14 0.11 0.01 14 ~ epotted gar 0.11' O.08-0.03 29 longnose gar oowfin 0.33 0.25 0.11 0.78 0.56 0.42 0.08 0.35 100 skipjack herring 0.08 0.22 0.11 0.05 43 - gizzard shad 0.08 1.00 0.11 0.25 1 33 0.40 71 0.08 0.01 14 goldeye 0.50 0.11 0.11 0.42 0.17 57 carp 0.11 0.33, 0.08 0.08 43 - river carpsucker smallmouth buffalo 0.17 0.11 0.56 1.33 0.17 0.35 71 0.11 0.58 0.11 29 bigmouth buffalo ,.g 1ue catfish 0.08 0.78 0.78 0.67 0.17 0.33 0.36 6 N 0.11 0.01 14 \\ Jackbullhead flathead catfish 0.33 0.11 0.33 0.08 0.50 0.20 71 0.08 0.01. 14 _ white bass 0.08 0.01 14 striped bass 0.08 0.01 14 largemouth bass white crappie 0.25 0.67 0.25 0.19 43 0.08 0.01 14 i - black crappie freshwater drum 0.08 0.11 0.44 0.42 0.33 0.20 71 Total 0.58 1.67 2.11 2.89 3.56 5.17 3.08 2.71 Effort 12 12 9 9 9 12 12-(net-days) i g ~

r 87 ( - Table 43. Catch / Effort (numbers and weights per net-day) of fishes taken in hoopnets at Mississippi River Stations, 1974 - 1975. NUMBERS Spring Summer Fall Winter Spring Summer Fall 1974 1974 1974 1975 1975 1975 1975 Mean Frequency gidzard shad 0.08 0.01 14 carp 0.03 0.01 14 river carpsucker 0.04 <0.01 14 _. ema11 mouth buffalo 0.04 0.04 0.01 29 black bullhead 0.04 <0.01 14 yellow bullhead 0.04 <0.01 14 flathead catfish 0.08 0.04 0.02 29 ~~ white bass 0.04 < 0. 01 14 white crappie 0.04 <0.01 14 freshwater drum 0.08 0.04 0.03 0.25 0.06 57 ~ Total 0.13 0.08 0.21 0 0.17 0.21 0.25 0.14 Effort 24 24 24 24 24 24 24 -(,) (net-days), W E I G H T S (1bs) ~ Spring Summer Fall Winter Spring Summer Fall i 1974 1974 1974 1975 1975 1975 1975 Mean Frequency - gizzard shad 0.05 0.007 carp 0.39 0.056 river carpsucker 0.01 0.018 - smallmouth buffalo 0.10 0.05 0.023 black bullhead-0.05 0.007 yellow bullhead 0.05 'O.007 _ flathead catfish 0.15 0.04 0.028 white bass 0.05 0.007 i white crappie 0.03 O.005 freshwater drum 0.12 0.05 0.08 0.34 0.083 Total 0.22 0.08 0.16 0 0.25 0.51 0.34 0.223 Effort 24 24 24 24 24 24 24 (net-days) .) t e

86 ' s, rw s _k_ Tcbic 42, Catch / Effort (pounds per net-day) of fishes taken in trammel nets at i Mississippi River Stations, 1974 -1975. l Spring Summer Fall Winter Spring Summer Fall ~ 1974 1974 1974 1975 1975 1975 1975 Mean chovelnose sturgeon 0.11 0.10 0.19 0.11 0.07 - paddlefish 0.06 <0.01 0.46 0.05 epotted gar 0.40 0.86 0.19 longnose gar - - - bowfin 1.58 1.32* 0.56 2.38 2.98 2.83 0.50 1.71* ekipjack herring 0.04 0.22 0.03 0.03 d zzard shad 0.03 0.67 0.11 0.14 1.56 0.37 i 0.03 <0.01 _ goldeye 1.30 0.20 0.42 1.97 0.60 carp 0.11 0.40 0.13 0.10 river carpsucker cma11 mouth buffalo 0.34 0.09 0.73 1.83 0.30 0.49 0.39 0.75, 0.17 ~ bigmonth buffalo blue catfish 0.73 1.13 1.09 1.37 0.40 0.71 0.73 bicck bullhead 0.06 <0.01 lathead catfish 0.98 0.09 0.88 0.15 1.26 0.50 0.13 0.02 tite bass 0.18 0.03 ctriped bass -- largemouth bass white crappic 0.28 0.63 0.18 0.17 0.08 <0.01 black crappie freshwater drum 0.08 0.17 0.39 0.34 0.22 0.17 Total 2.46 4.33 2.51 4.48 8.38 10.70 4.87 5.42 ~ Effort 12 12 9 9 9 12 12 (net-days)

Some or all specimens too decomposed for accurate weight.

i 1 -- M l ~. f~ ~ / 1 ~ 1

88 () Table 44. Catch / Effort (number per seine-hour) of fishes collected at ,~ Alligator Bayou Station 1, 1974 - 1975. Summer Fall Summer. Fall 1974' 1974 1975 '1975' Mean' Frequency gizzard sbad 16.0 2.0 1.3 4.17 75 grass pickerel 2.0 0.42 25 , silvery minnow 3.3 14.0 8.8 6.67 75 ~ ( silver chub 2.0 0.42 25 ~ golden shiner 10.0 2.08 25 emerald shiner 20.0 10.0 7.50 50 river shiner 1.3 0.42 25 ribbon shiner 11.7 44.0 105.0 47.08 75 longnose shiner 5.0 1.67 25 weed shiner 2.0 10.0 2.50 50 blacktail shiner 8.0 63.3 2.0 17.92 75 pugnose minnow 6.0 10.0 3.33 50 - river carpsucker 2.0 0.42 25 smallmouth buffalo 2.0 0.42 25 bigmouth buffalo 4.0 O.83 25 pirate perch 1.7 - 0.42 25 blackspotted topminnow 10.0 2.5 2.92 50 l mosquitofish 10.0 5.0 4.17 50 0.42 25 \\ brook silverside 2.0 2.08 50 warmouth 8.0 1.7 bluegill 10.0 16.7 2.0 3.8 7.97 100 longear sunfish 18.0 5.0 6.0 6.25 75 spotted s'udfish 1.3 0.42 25 largemouth bass 2.0 1.7 2.0 1.3 1.67 100 a black crappie 6.0 2.0 1.67 50 freshwater drum 1.7 0.42 25 98.0 116.7 126.0 145.0 124.17 Total i Effort 0.5 ~0.6 0.5 0.8 (seine-hours) 4 t JD 8 r

89 Table 45. Catch / Effort (number per gear-hour) of fishes collected at Alligator Bayou Station 3 (" Grassy Lake"), Summer and Fall, 1974 - 1975. - Ssines' 'Electrofishing Summer Summer-Fall 1974 1975 1975 spotted gar 1.3 2.5 5.7 ~ bowfin 6.5 gizzard shad 2.5 1.3 23.9 carp 2.5 7.0 golden shiner 1.3 emerald shiner 1.3 ribbon shiner 20.0 pugnose minnow 5.0 river carpsucker 4.8 smallmouth buffalo 6.5 bigmouth buffalo 1.7 spotted sucker 0.4 black bullhead 3.5 yellow bullhead 5.0 7.8 pirate perch 1.3 ~~(q ./ blackspotted topminnow 2.5 6.3 mosquitofish 21.3 brook silverside 2.5 1.3 flier 5.0 4.8 warmouth 8.8 1.3 19.1 bluegill 11.3 13.8 29.1 longear sunfish 1.3 2.2 redear sunfish 2.5 1.3 spotted sunfish 0.4 largemouth bass 22.2 white crappie 15.0 8.8

1. 7, black crappie 85.0 12.5 10.4 bluntnose darter 1.3 4

freshwater drum id.9' ~ i - Total 145.0 98.8 170.4 Effort 0.8 0.8 (gear-hours) O t D

90 O ~lu / Table 46. Catch / Effort (number per seine-hour) of fishes collected at Alligator Bayou Station 4, 1974 - 1975. Spring Summer Fall Winter Summer Fall 1974 1974 1974 1975 1975' '1975' 'Mean-Frequency , gizzard shad 0.8 0.16 17 ~ i grass pickerel 2.0 0.33 17 silvery minnow 1.0 2.7 0.8 0.82 50 t golden shiner 6.3 1.1 0.98 33 ribbon shiner 9.0 41.3 24.4 27.3 184.0 61.5 58.69 100 3.1 3.44 33 blacktail shiner 15.5 smallmouth buffalo 0.8 0.16 17 yellow bullhead 1.1 1.8 1.0 0.66 50 pirate perch 7.0 2.2 27.3 6.39 50 blackspotted topminnow 2.0 5.0 3.6 12.0 7.7 5 25 83 mosquitofish 26.0 15.0 14.4 7.3 19.0 23.,8 1*/.87 100 flier 1.3 0.16 17 warmouth 23.0 3.8 4.4 3.6 1.0 5.74 83 ~ banded pygmy sunfish 0.8 0.16 17 s bluegill 21.0 26.3 1.1 0.9 12.0 3.9 10.00 100 s_ dollar sunfish 1.0 1.3 0.33 33 ~~ longear sunfish 5.0 2.2 2.7 1.0 0.8 1.80 83 spotted sunfish 3.0 2.5 0.9 2.0 0.8 1.48 83 largemouth bass 1.3 0.9 1.0 1.5 0.82 67 black crappie 3.0 0.49 17 mud darter 2.0 2.5 10.0 6.4 11.0 8.5 6.88 100 Total 97.0 111.2 61.1 100.9 247.0 114.6 122.62 Effort 1.0 0.8 0.9 1.1 1.0 1.3 (seine-hours) 1 I W e ~... .n 7---

I i i f f I I I i I i I i t i i O O O Table 47. Comunity structure of fishes at Alligator Bayou stations, 1974 - 1975, as reflected by ranking in descending order of relative abundance (catch / effort) the species comprising 90% of total" specimens collected at each station. c Station 1 Station 3 Station 4 Seines Seines Electrofishing Seines ribbon shiner black crappie bluegill ribbon shiner blacktail shiner bluegill gizzard shad mosquitofish bluegill white crappie largemouth bass bluegill c=erald shiner mosquitofish warmouth mud darter silvery minnow ribbon shiner freshwater drum pirate perch longear sunfish warmouth black crappie warmouth gizzard shad blackspotted topminnow yellow bullhead blackspotted topminnow mosquitofish pugnose minnow carp blacktail shiner pugnose minnow yellow bullhead bowfin longear sunfish blackspotted topminnow flier smallmouth buffalo spotted sunfish weed shiner spotted gar warmouth river carpsucker flier golden shiner 10 species 13 species 18 species l i e

92 Table 48. Catch / Effort (number per' seine-hour) of fishes collected at Grants Bayou Stations, 1974.- 1975. S'T A T I'O'N' 'l Fall Winter Spring Summer 1974 1975 1975 1975' Mean' Frequency gizzard shad 1.1 0.42 25 golden shiner 5.6 12.0 2.0 5200' 75 striped shiner 2.0 0.42 25 blacktail shiner 4.0 0.83 25 creek chub 5.6 4.0 2.92 50 creek chubsucker 2.0 0.42 25 '~ black bullhead 1.1 2.0 0.83 50 2.0 0.42 25 yellow bullhead 8.0, 4.0 28.0 9.17 100 blackspotted topminnow 2.2 mosquitofish 20.0 58.0 84.0 74.0 52.50 100 green sunfish 10.0 2.0 2.50 50 bluegill 5.6 142.0 28.0 48.0 47.50 100 largemouth bass 12.0 2.0 ,2.92 50 Total 41.1 240.0 128.0 162.0 125.83 ~['} Effort 0.9 0.5 0.5 0.5 \\_/ (seine-hours) STATION '2 Fall Winter Spring Summer i 1974 1975 1975 1975 Mean ' Frequency golden shiner 5.6 5.7 3.3 50 creek chub 1.7 0.37 25 creek chubsucker 1.4 0.37 25 black bullhead 1.4 1.7 0.74 50 yellow bullhead 10.0 1.85 25 blackspotted topminnow 14.4 1.4 10.0 12.59 75 mosquitofish 7.8 25.7 21.7 66.0 26.30 -100 green sunfish 1.4 3.3 4.0 1.85 75 g bluegill 14.4 194/3 45.0 10.0 67.04 100 largemouth bass 2.2 2.9 6.7 2.0 3.3 '100 Total 44.4 234.3 90.0 92.0 112.59 Effort 0.9 0.7 0.6 0.5 (seine-hours) +

93 ~ (] AMPl!IBIANS AND REPTILES Table 49 lists the amphibians and reptiles observed' on and near the River Bend study area during the first seven' quarters of the interim monitoring program. The list follows modern classification and nomenclature as presented by Keiser and Wilson (1969), which reflects numerous changes from the system used in the herpetology section of the~ Environmental Report (ER). During interim monitoring 66 species were observed, including 10 sala-manders, 12 frogs, the American alligator, eight lizards, 23 snakes, and 12 turtles. Seven of these were not listed as known or expected for the study area in the ER (three-lined salamander, central newt, ground skink, Mississippi ~ mud turtle, keel-backed musk turtle, southern painted turtle l smooth soft-shell turtle). Four species, listed as "probably present" in the ER, were () not observed during 1974-75 (spotted salamander, spadefoot toad, rainbow snake, Graham's water snake). Observations on the herpetofauna of River Bend were only made incidental I ~ to other (primarily aquatic) field work. In Table 49 species are listed as " common" only if they were observed and/or captured regularly in the habitats in question. " Rare" forms are those observed at least once, but fewer than three times during the two-year period. Many of the more secretive species i (e.g. Ambystoma salamanders, several small snakes) would probably prove to be common at River Bend if concerted searching efforts were used. J W C e

94 (~/1 Table 49. Amphibians and reptiles observed on and near River Bend study area, 1974-75. \\- Forms marked by asterisk were not recorded in earlier reports. (C= common; R= rare; species listed under " River" are only the primarily-aquatic forms - many of the amphibicus or largely terrestrial forms listed under " Lowland" occur along the river banks.) River Lowland Upland Ambystoma opacum (Gravenhorst) - marbled salamander R R A,. talpoideum (Holbrook) - mole salamander R Amphiuma tridactylum Cuvier - three-toed amphiuma R C Nieturus beyeri beyeri Viosca - Gulf Coast waterdog R R Desmognathus auriculatus (Holbrook) - dusky salamander R Eurycea longicauda guttolineata (Holbrook) - three-lined salamander

R Manculus quadridigitatus (Holbrook) - dwarf salamander R

Plethodon glutinosus (Green) - slimy salamander R R Notophthalmus viridescens louisianensis (Wolterstorff) - central newt

C Siren intermedia nettingi Coin - western lesser siren '

C Bufo valliceps Wiegmann - Gulf Coast toad C C / C C ~ B. voodhousei fowleri Hinckley - Fowler's toad Acris crepitans Baird - cricket frog C C Hyla cinerea (Schneider) - green treefrog C C H R C g _. crucifer Wied - spring peeper R C (,jH. squirella Sonnini and Latreille - squirrel treefrog C C H. versicolor _LeConte - gray treefrog Pseudacris triseriata feriarum - western chorus frog C C Gastrophryne carolinensis (Holbrook) - eastern narrow-mouthed toad C Rana catesbiana Shaw - bullfrog C C R. clamitans Latreille - bronze frog C R [.pipienssphenocephalaCope-southernleopardfrog C C Alligator mississipiensis (Daudin) - American alligator R C R R Ophisaurus ventralis (Linnaeus) - eastern glass lizard -u- '~ Anolis carolinensis Voight - Carolina anole C C Sceloporus undulatus (Latreille) - fence lizard R C Cnemidophorus sexlineatus (Linnaeus) - six-lined raccrunner R Eumeces fasciatus (Linnaeus) - five-lined skink C E. inexpectatus Taylor - southern five-lined skink. R -1.-laticeps (Schneider) - broad-headed skink R Scincella laterale (Say) - ground skink

C C

I Celuber constrictor priapus Dunn and' Wood - southern black R C racer ~ Diadophis punctatus strictogenys Cope - Mississippi ringneck snake C Elaphe guttata (Linnaeus) - corn snake C Farancia abacura reinwardti Schlegel - western mud snake C R Heterodon platyrhinos (Latreille) - eastern hognose snake R C fsLampropeltis getulus holbrooki Stejneger - speckled king-D snake C C 6 +v.

Table.49. Continued. 95 River Lowland Upland . triangulum amaura Cope - Louisiana milksnake R _Masticophis_ flagellum (Shaw) - eastern coachwhip R C Natrix cyclopion (Dumeril et al.) - green water snake R C R N. ery_throgaster flavigaster Conant - yellow-bellied water snake R N. rhombifera (Hallowell) - diamondback water snake C N. sipedon pleuralis (Cope) - midland water snake C C C Opheodrys aestivus (Linnaeus) - rough green snake C C Storeria dekay1 wrightorum Trapido - midland brown snake R Tantilla coronata Baird and Girard - crowned snake R Thamnophis proximus (Say) - western ribbon snake R C C ];. sirtalis (Linnaeus) - eastern garter snake R R Virginia striatula (Linnaeus) - rough earth snake R C Agkistrodon contortrix (Linnaeus) - southern copperhead R C A. pisciverus leucostoma (Troost) - western cottonmouth R C C Crotalus horridus atricaudatus Latreille - canebrake rattlesnake C C 0 _ Sistrurus miliaris streckeri Gloyd - western pygmy rattle-snake R Micrurus fulvius fulvius (Linnaeus) - eastern coral snake R - Chelydra serpentina (Linnaeus) - common snapping turtle R C R Kinosternon subrubrum hippocrepis Gray - Mississippi mud turtic* R ' crocle=mys te=mincki (Troost) - alligator snapping turtle R a 'ternothaerus carinatus (Gray) - keel-backed musk turtle

R S. odoratus (Latreille) - stinkpot

~R C C - _Chrysemys picta dorsalis Agassiz - southern painted turtle

R C

C,. concinna mobilensis (Holbrook) - Mobile cooter R R R C. scripta elegans (Wied) - red-eared turtle R. C' C _ Craptemys Kohni (Baur) - Mississippi map turtle C R Terrapene carolina triunguis (Agassiz) - three-toed box turtle R C Trionyx cuticus LeSueur - smooth softshell turtle

R R

~ ];. spinifer asper (Agassiz) - Gulf coast spiny softshell turtle C R R ~ f O

96 ~ LITERATURE CITED Keiser, E. D., Jr. and L. D. Wilson.1969. Che~cklist and Key to the herpetofauna of Louisiana. Tech. Bull. 1, Lafayette Nat. Hist. I Mus., 51 p. Lind, O. T. 1974. Handbook of common methods in Limnology. C. V. Mosby l Co., St. Louis. vil + 154 p. E Wilding, J. L.1940. A new square-foot sampler. Spec. Pubis. Limnol. Soc. Amer. 4(4):238. l I / O N >om p m G m e me hum w t ._}}

ML20042B475

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