American Eel Distibution and Growth in Selected Tributaries of the James River
Strickland, Patrick Andrew
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Distribution and Growth of American Eels in Selected Tributaries of the James River by Patrick Andrew Strickland Committee Chair: C. Andrew Dolloff Fisheries and Wildlife Sciences Abstract In July of 1999, a team of researchers from the Virginia Department of Game and Inland Fisheries (VDGIF) and the United States Forest Service (USFS) electrofished a 2-km reach of Shoe Creek, Virginia, and captured 66 American eels. Eels were weighed (g) and measured (mm) and 61 individuals were implanted with Passive Integrated Transponders (PIT). Size distribution of the tagged eels ranged from 174-775 mm total length. The team returned to Shoe Creek in October of 1999 for a recapture survey, but captured only seven eels in the same 2-km reach with no recaptures. This sparked considerable interest among the biologists of VDGIF and USFS. Goals of the biologists included identifying daily movement, seasonal distribution, relative abundance, habitat use, and growth of American eels in Virginia headwater streams. This information was needed for the protection of eel habitat and migration corridors, as well as development of restoration plans for eels. Seasonal movement of thirty-three American eels Anguilla rostrata was monitored from July 2000 through September 2001 via radio telemetry. South Fork Piney River, South Fork Tye River, and Shoe Creek, Virginia were the streams chosen for eel research. Eels exhibited the greatest amount of movement in summer 2000 and the least amount of movement in winter 2000-01. Diel activity was significantly lowest in winter 2000-01 and highest in spring 2001. From late October 2000 through May 2001, eels appeared to be buried within the interstitial spaces of the stream bottom and under stream banks. Habitat preference (average depth, dominant substrate, and pool vs. riffle) was also determined over multiple seasons via radio telemetry. When a preference was detected, eels always preferred pools and the deepest water available relative to each stream. Eels preferred cobble as the dominant substrate during all seasons in S.F. Tye River. Eels showed no preference for substrate in S.F. Piney River. Substrate preference varied among seasons in Shoe Creek. Estimates of 12, 41, and 25 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2000. There was a significantly higher density of eels in S.F. Tye River when compared to S.F. Piney River in summer 2000. Estimates of 7, 54, and 15 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2001. There was a significantly higher density of eels in S.F. Tye River when compared to both S.F. Piney River and Shoe Creek in summer 2001. Growth in total length (TL) was determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in TL for S.F. Piney River, S.F. Tye River, and Shoe Creek was 18, 23, and 21 mm/year, respectively. Growth in TL for Shoe Creek was also calculated from 1999-2000 (43 mm/year) and 1999-2001 (32 mm/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01. Growth in weight was also determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in weight for S.F. Piney River, S.F. Tye River, and Shoe Creek was 24, 21, and 27 g/year, respectively. Growth in weight for Shoe Creek was also calculated from 1999-2000 (50 g/year) and 1999-2001 (40 g/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01. Our results have contributed to knowledge of the biology and ecology of the American eel in the upper James River drainage, including diel activity, seasonal movements, habitat use, densities, and growth. Eels were more active during spring and summer, particularly at night. They demonstrated very little movement throughout the other seasons of the year. The majority of eels displayed a behavior similar to hibernation, burying in the substrate and under the banks of the stream from mid-fall through mid-spring. Eels showed a trend to use deep pools with large substrate throughout the majority of this study. Eel densities seemed to vary among streams, with higher growth in streams with lower eel densities and a higher average water temperature.
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