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Title: Behavioral responses of anadromous Blueback Herring and American Shad to high-frequency sound, flow and a wing wall in St. Stephen Tailrace, South Carolina
Authors: Ploskey, Gene R.
Pickens, James L.
Weeks, Gary N.
Keywords: Fishes--Behavior
Blueback herring
American shad
Publisher: Environmental Laboratory (U.S.)
U.S. Army Engineer Waterways Experiment Station.
Series/Report no.: Technical Report ; EL-94-7
Abstract: In March 1992, we used fixed-aspect hydroacoustics in St. Stephen tailrace to monitor responses of fishes (mostly anadromous blueback herring and American shad) to high-frequency (118 kHz) sound, flow, and the north wing wall. A 118-kHz transducer was aimed 4.6 m below the end of the north wing wall from a location 20 m downstream and near the north bank. It was used to guide fish around the end of the wing wall, which was believed to be an impediment to the movement of fish to the fish lift on the north side of the tailrace. However, 5 days of sampling clearly revealed that the wall does not hinder the movement of fish around the end of the wall. Observations of fish behavior were made during generation limited to the two turbines on the south side of the tailrace. Over 80 percent of targets observed moving upstream against current encountered a 0.3- to 0.7-m/sec eddy and followed it around the end of the wall rather than entering the area behind the wing wall, on "sound on" and "sound off' days. The eddy moved from the north bank, 20 m below the end of the north wing wall, to and around the end of the wall, and back toward the fish lift and St. Stephen Dam. The mean percent passage around the north wall on days when 118-kHz sounds were transmitted (119 percent) did not differ significantly from that observed on control days when no 118-kHz sounds were transmitted (83 percent). A conservative estimate of total passage would be about 1,314 fish/hour, assuming we sampled all depths that contained fish (the top 42 percent) but only one-third of the width they might have passed through. Cast netting from the end of the north wing wall , occasionally at targets tracked with hydroacoustics, captured nine American shad, five blueback herring, and one mullet. No debris was collected. Electroshocking showed that the ratio of the number of alosids to the number of "other" fishes in area behind the north wing wall was low at 1030 hr (0.03) and 1330 hr (0.1) but much higher from 1530 to1900 hr (4.9 to 25.3) while we tracked fish. Noise associated with turbulent flow during three-unit generation prevented us from tracking fish in the vicinity of the wall from 1900 to 1400 hr daily. Three-unit generation did not affect our sampling of fish density in the sheltered area behind the wing wall. Echo-integration data show that densities of fish behind the wall were 10 to 24 percent lower on days where 118-kHz sounds were transmitted than they were on silent days. Given patterns of fish movement observed on all days of sampling, we do not recommend the installation of a high-frequency sound system to guide fish or any alteration of tailrace wing walls solely to remove these supposed impediments to upstream movements of fish. However, our results clearly show how important flow patterns are to fish navigating the tailrace of St. Stephen Dam and how adept fish are at using them . Our only reservation about the results is that the fish lift, which normally would have released 200- to 310-cfs flows along the north wing wall to attract fish, was not operable in early March when our surveys were conducted. How attraction releases might have changed flow patterns in the area of the north wing wall or the behavior of fish is not known.
Description: Technical Report
Gov't Doc #: Technical Report EL-94-7
Rights: Approved for Public Release; Distribution is Unlimited
Size: 70 pages/23.99 Mb
Appears in Collections:Technical Report

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