ML073240726
| ML073240726 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/31/1993 |
| From: | Collins M R, Smith T I State of SC, Dept of Natural Resources |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NL-07-2097 | |
| Download: ML073240726 (7) | |
Text
Characteristics of the Adult Segment of t Savannah River Population of Shortnos Sturgeon 1.Mark R.Collins, Marine Resources Research Ins tute, S.C.Department of Natural Resources, P.O.Box 1.'2559, Charleston, SC29422 Theodore I.J.Smith, Marine Resources Rese rch Institute, S.C.Department of Natural Resources, P.O.Box 12559, Charleston, SC29422 Abstract: During 1984-1992,626 adult shortnose sturgeon (3.5 male:l female)were captured in the Savannah River.Significantly more fish were aptured in the lower (rkm 42-75)than the upper (rkm 160-299)river..'.*." ,t".ltl1ted that orne an Ividuals spawned in consecutive years, but others apparently did not.Nonspawning fish appeared to remain in the vicinity of the fresh/brackish water interface (ca.rkm 30-40) out the spawning season.Most shortnose sturgeon left the freshwater reaches of the river in Spring soon after the spawning season (January-April) and probably did not return until late Autumn/early Winter, just prior to the spawning season.Proc.Annu.Conf.Southeast.
Assoc.Fish and Wildt.Agencies 47:485-491 The shortnose sturgeon, Acipenser brevirostrum, inhabits large coastal rivers from New B.runswick, Canada, to northern Florida (Vladykov and Greeley 1963).Prior to 1973 this species was harvested concurrently with, and not distinguished from, Atlantic sturgeon (A.oxyrinchus).
Today it is liste4 as an endangered species in the United States, but recent undercover law enforcement work indicates that it is still illicitly taken for its flesh and eggs (caviar).The biology of shortnose sturgeon in the northern portion of its range has been the focus of several studies (Dadswell 1979, Taubert 1980, Buckley and Kynard 1985), but relatively little information is available concerning the biology'This research was sponsored by the U,S.Department of Interior, Anadromous Fish Conservation Act, Project No.
17, and by the State of South Carolina.Reference to trade names does not imply endorsement.
This is contribution No.328 from the South Carolina Marine Resources Center.1993 Proc.Annu.Conf.SEAFWA Methods of this species in southern rivers.During 1984-1992 the South and Marine Resources Department (now the S.C.Department of Naturalsources)and the United States Fish and Wildlife Service conducted a cooperative study of shortnose sturgeon in the Savannah River.This paper reports on various aspects of the biology of adult shortnose sturgeon inhabiting the Savannah River.We gratefully acknowledge the assistance of Elizabeth Kennedy, Charles Bridgham, and Allan Hazel in data collection.
We also appreciate the comments of William Roumillat and an anonymous reviewer.1993 Proc.Annu.Conf.SEAFW A Figure 1.Length , i 1ft:p, 85!frequency of Savannah";'.,..i River shortnose sturgeon....1:i., co crt....c captured in gill nets.,..Total Length (em)during 1984-1992.
160 140'I 12010080'0.I 60 E:::s Z 40 20 0 The Savannah River was selected as the study site based on reports ofdental captures of adult shortnose sturgeon in the shad gill net fishery.This river delineates much of the South Carolina-Georgia border and flows into the Atlantic Ocean near the city of Savannah, Georgia.The river is impounded at several sites, and the present study was conducted.in the ca.300 kIn between the mouth and first obstruction, the New Savannah Dam near Augusta, Georgia.The upper river area (URA;river kilometers (rkm)160-299)is relatively undeveloped with thetion of 2 major nuclear facilities; the Savannah River Site in South Carolina and Plant Vogle in Georgia.The lower river area (LRA;rlan 42-75)is similarlyveloped, but it is just upriver from the heavily industrialized port and harbor area of the city of Savannah.Adult shortnose sturgeon (defined as cm total length (TL)based onamination of broodstock) were collected during 1984-1992 from the study area by 486 Collins and Smith r 1Io.Savannah River Shorlnose Sturgeon 487 2 commercial shad fishermen.
During the legal shad season (typically mid-January to mid-April), 1 individual fished the URA while the other fished the LRA.Fishing effort was similar in all years except 1984, when the LRA was not fished, and 1992, when only minimal effort was expended in the URA.Both fishermen used anchored monofilament gill nets of 14 cm stretch mesh.Nets were checked daily, and all sturgeon were placed in floating, cylindrical pens of plastic mesh.Project personnel removed captured sturgeon from the pens 1 to several times per week, depending on catch rates.The captured fish were used for a variety of purposes.Many shortnosegeon, especially suspected ripe or nearly ripe individuals, were transported to Orangeburg National Fish Hatchery for spawning as part of a stock enhancement program (Smith et aI.1985, 1995).After 1-3 months, these fish were tagged and released into the Savannah River.Prior to 1991 fish were classified as ripe based on degree of abdominal distention, if gametes could be easilyexpressed,or if the vent was obviously everted.During 1991-1992 gonadal tissue acquired through biopsy was examined grossly and/or microscopically to determine stage of ripeness.Shortnose sturgeon not used as broodstock and some incidentally caught Atlantic sturgeon were marked with one or more tag types and released.When possible these fish were assigned a sex and maturity stage.Data on sex ratios and numbers of fish captured were statistically analyzed using the Chi-square test with P<.05 requir.ed for significance.
In order to identify spawning areas and other critically important habitats, some shortnose sturgeon were utilized in radio telemetry studies during 1990-1992.
Transmitters were 70 mm long x 18 mm diameter and operated in the 48-50 Mhz range.Transmitter lifespan was estimated by the manufacturer to be 475 days.The transmitters were surgically implanted into the abdominal cavity through a ventral, Thble 1.Number of Savannah River shortnose sturgeon captured in lower (RKM 42-75)and upper (RKM 160-299)river areas bycommercial shad fishermen from 15 January-IS April 1986-1992 and percentage of sexed fish that were spawningtion (running ripe and or evidence of protruding vent during 1986-1990, andnation of gonadal tissue during 1991-1992).
Total number includes fish of unknown sex and maturity stage.Maturity stages were not recorded in 1984 and 1985.Lower river Upper river Total Females Males Total Females Males Year Nfish N%Ripe N%Ripe Nfish N%Ripe N%Ripe 1984 25 3 22 1985 49 6 43 62 15 47 1986 36 5 40 31 50 tt 1 100 10 40 1987 31 7 100 21 to 27 5 100 21 19 1988 53 13 23 31 23 29 8 75 21 67 1989 54 2 50 46 37 40 9 78 30 40 1990 55 5 60 20 25 34 7 71 26 50 1991 99 16 63 22 100 16 2 100 13 100 1992 35 15 47 6 100 1 0 0 I 100 1993 Proc.Annu.Conf.SEAFWA 4UlS t..:omns and:Smith Table 2.Size (total length), site (river kilometer) and date of release, and site and date of the relocation farthest upriver for Savannah River shortnose sturgeon tracked by radio telemetery during 1990-1992; 5 addi-tional individuals were not relocated after the day of release.Release Relocation TI...(cm)Date Site (rkm)Date Site rIan)84.0 02 Mar 90 46.1 13 Apr 90 46.8 78.0 15 Mar 90 46.1 29 Mar 90 50.0 80.0 20 Mar 90 46.1 13 Apr 90 218.8 76.8 20 Mar 90 46.1 23 Mar 90 46.1 89.5 20 Mar 90 46.1 21 Mar 90 36.0 106.2 22 Jan 91 46.1 28 Jan 91 227.9 85.5 22 Jan.91 46.1 21 Feb 9J 221.6 97.0 22 Jan 91 46.1 20 Feb 91 220.9 70.0 26 Jan 91 46.1 01 Feb 91 41.7 81.2 29 Jan 91"46.1 01 Feb 91 43.2 84.9 05 Feb 91 46.1 25 Feb 91 188.4 83.9 05 Feb 91 46.1 28 Feb 91 212.8 82.1 05 Feb 91 46.1 27 Feb 91 179.3 86.2 05 Feb 91 46.1 27 Feb 91 187.4 89.5 12 Feb 91 46.1 27 Feb 91 134.1 85.2 12 Feb 91 46.1 27 Feb 91 181.6 87.2 12 Feb 91 46.1 19 Feb 91 45.0 87.0 12 Feb 92 48.0 20 Feb 92 208.0 midline incision which was closed with Ethicon 00 sutures.Tracking wasductedboth from boat and airplane using programmable scanning receivers (Advanced Telemetry Systems, Isanti, Minn.).Tracking efforts were initiated when transmitter-equipped fish were released.Searches were conducted daily to weekly until approximately mid-April.
Weather dependent, bimonthly searches continued through the summer, and thereafter occurred irregularly.
Results During 1984-1992, 626 adult shortnose sturgeon were captured by the 2 commercial shad fishennen (Table 1).Lengths ranged from 56 to 107 cm TL, and the modal size class was 71-75 cm TL (Fig.1).Nineteen percent were female, 66%were male, and the remaining 15%were of undetermined sex.Numbers of fish captured per year ranged from 1 to 62 (mean+/-sd=27.2+/-17.7)in the URA and 31-99 (51.5+/-21.4)intheLRA.During 1985-1991, significantly (P<.001)more fish were captured in the LRA (377)than the URA (219).The ratio of males to females varied annually from 0.4: 1 to 23: 1 in the LRA and from 2.6: 1 to 10: 1 in the URA.Overall ratios were not significantly different:
3.2: 1 in the LRA and 3.8: 1 in the URA.The pooled sex ratio was 3.5 males: 1 female.The percentages of females classified as ripe were 81%and 53%in the URA and LRA, respec-1993 Proc.Annu.Conf.SEAFWA Savannah River Shortnose Sturgeon 489 tively, and the percentages for ripe males were 50%and 42%, respectively.racy of the percentages, especially for males, is somewhat in doubt due to the higher percentage (100%)classified as ripe through the biopsy method compared to the method used in previous years (Table 1).Ninety-five percent of the fish of unknown sex and maturity stage were captured in the LRA.Juvenile Atlantic sturgeon co-occurred with adult shortnose sturgeon during January-April in the LRA, but not in the URA.In 1990, 3 Atlantic sturgeon were captured, while 6 were caught in both 1991 and 1992.Data on capture of juvenile Atlantic sturgeon were not recorded during previous years.Eight fish were used successfully as broodstock and recaptured in following years.Of these, 1 female and 6 males were again used successfully.
The female spawned after an interval of only 1 year (Le., in 2 consecutive spawning seasons), and 2 males did likewise.Three males were ripe again after 2 years and*1 after 3 years, but whether they spawnedinintervening years is not known.The eighth fish was a male which was unripe when recaptured after an of 1 year.Twenty-four radio transmitters were implanted into adult shortnose sturgeon.With the exception of 1 indi vidual captured and released in the URA in 1990, all fish used in radio telemetry efforts were captured and released in the LRA (Table 2).Ten of the 23 fish from the LRA ascended to the URA, and 1 ascended part way (to rkm 134)where contact was lost.Seven fish were relocated in or just below the LRA, while contact was lost immediately with 5 fish.Nine of the 15 fish (60%)planted and released prior to mid-February ascended to the URA, compared to only 1 of the 8 (12.5%)released afterward.
The maximum upriver locations (rkm)of these 10 fish were: 179, 182, 187, 188,208,213,219, 221,222, and 228.The 7 fish that were only detected in the LRA vicinity were recorded between rkm 36 and rkrn 46 for 1 to 42 days.No fish were located later than mid-April in either the LRA or URA, and no fish were located in years other than that of release.Discussion Relative abundance of shortnose sturgeon was significantly greater in the LRA than in the URA.This may be due in part to the fact that fish migratingriver to spawn are vulnerable to capture in the LRA during both the upriver and downriver segments of the migration.
Nearly all fish that were considered notably ripe for use as broodstock were captured in the LRA, suggesting that each year some portion of the population neither spawns nor participates in the upriver migration.
These fish possibly remain in the LRA, or just below in slightlyish water, throughout the spawning season and are therefore vulnerable to capture over an extended period.It is also possible, however, that fishing effort of 1 or both of the commercial shad fishennen varied without our knowledge in somestances, thus confounding our interpretation of the relative abundance data.Telemetry data also suggest that only a portion of the population participates in the upriver spawning migration.
For example, 30%of telemetered fish remained in or just downriver from the LRA, while 22%were never relocated after the day of re-1993 Pree.Annu.Conf.SEAFWA
.., ,490 Collins and Smith lease.Although failure to locate these fish may be attributable to transmitter failure in some instances, it is that at least some individuals crossed to the saline side of the freshlbrackish water interface, thereby attenuating the radio signals.Thus, the hypothesis that the freshlbrackish water interface area and the downriver portion of the LRA serve as a staging area for the spawning migration and a holding area for fish that do not participate in the upriver migration is supported by telemetry, relative abundance, and maturity stage data collected in this study.Migrating shortnose sturgeon began upriver in late January toMarch, traveling at average speeds of up to 50 km per day.Hall et al.(1991)reported upriver migration in the Savannah River during February and March at speeds of 1-33 km per day.: ".....,....",'{""."",
in the q1:'tl..
- the Saint John shortnose later (May-June), but at similar tem-peratures (Dadswell 1976).Hall et aI.(1991)reported spawning behavior during March in the Savannah River, and identified 2 probable spawning areas: rkm 179-190 and rkm 275-278.Four of 10 fish that migrated upriver in the present study were recorded in the lower of these 2 areas.However, the other 6 fish moved to rkm 208-228.The stretch of river between rkrn 208 and 228 is similar to the probable spawning areas above and below (Hall et a1.1991), as it contains sharp bends with strong currents, submerged timber, and a substrate of gravel, clay, and sand.Areas of strong currents and scoured, coarse substrate provide the conditions believed necessary for successful spawning, egg attachment, and hatching.Sites with similar conditions and substrate are utilized as spawning habitats by shortnose sturgeon in the Saint John River, Canada, and the Connecticut River (Dadswell 1979, Buckley and Kynard 1985).Telemetry data suggest that most shortnose sturgeon left the freshwatertion of the Savannah River by mid'-ApriI.
This was also reported by Hall et al.(1991), who noted that shortnose sturgeon in the Savannah River had left fresh water by early May, although some remained in the vicinity of the freshlbrackish water interface through the summer.In contrast, in the northern portion of this species'range, from the Hudson River to the Saint John River, shortnose sturgeon apparently utilize freshwater habitats more extens'ively, with segments of some populations remaining in fresh water throughout the year (Dads well 1979, Buckley and Kynard 1985).Juvenile Atlantic sturgeon are occasionally captured at and just above the freshlbrackish water interface, but not upriver near spawning areas, during the shortnose sturgeon spawning season.
B.Kynard.1985.Yearly movements of shortnose sturgeon in theer.Trans.Am.Fish.Soc.114:813-820.
1976.Biology of the shortnose sturgeon, Acipenser brevirostrum, in the 1993 Proc.Annu.Conf.SEAFWA 1993 Proe.Annu.Conf.SEAFWA Saint John River estuary, New Bruswick, Canada.Trans.Atl.Chap.Can.Soc.ron.Biol.Annu.Meet.1975:20-72.
---.1979.Biology and population characteristics of the shortnose sturgeon Acipenser brevirostrum leSueur 1818 (Osteichthyes:
Acipenseridae) in the Saint John Estuary, New Brunswick, Canada.Can.J.ZooL 57:2186-2210.
Hall, J.W., T.I.J.Smith, and S.D.Lamprecht.
1991.Movements and habitats of shortnose' sturgeon, Acipenser brevirostrum in the Savannah River.Copeia 3:695-702.
Smith, T.I.J., E.K.Dingley, R.D.Lindsey, S.B.Van Sant, R.A.Smiley, and A.D.Stokes.1985.Spawning and culture of shortnose sturgeon, Acipenser brevirostrum.
J.World Maricult.Soc.16:104-113.
--, W.E.Jenkins, L.D.Heyward, and E.T.Kennedy.1995.Overview of experimental stocking program for shortnose sturgeon, Acipenser brevi rostrum ,inthe southeastern United States.Proc.World Fish.Congress Theme 3:273-277.
Taubert, B.D.1980.Reproduction of the shortnose sturgeon (Acipenser brevirostrum) in the Holyoke Pool, Connecticut River, Massachusetts.
Copeia 1980:114-117.
Vladykov, V.D.and J.R.Greeley.1963.Order AcipenseroideL Pages 24-60 in V.H.Olsen, ed.Fishes of the Western North Atlantic, Part ill.Memoirs of the Sears Found.for Mar.Res., New Haven, Connecticut.
,...Savannah River Shortnose Sturgeon 491