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<br />DIETARY TOXICITY AND STRIPED BASS
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<br />FIGURE I.-Location and hydrography ofBelews Lake,
<br />North Carolina. Sampling locations were (A) a 0.39-
<br />hectare cove used for rotenone sampling near the ash-
<br />basin discharge, (B) a 0.65-hectare, uplake, rotenone-
<br />sampled cove hydrologically isolated from the influence
<br />of the ash-basin effluent, and (C) Pine Hall boat access
<br />area, where red shiners were collected.
<br />
<br />golden shiners Notemigonus crysoleucas obtained
<br />from a local bait dealer. Striped bass were treated
<br />prophylactically for bacterial diseases and external
<br />parasites during acclimation and periodically
<br />throughout the experiment. After the initial accli-
<br />",mation period, striped bass were anesthetized (290
<br />mg tricaine/L), weighed (within 0.1 g), and mea-
<br />sured for total length (within I mm). Condition
<br />factor (K) was computed as IOs'weightlIengthJ.
<br />Ten striped bass were placed in each of three cir-
<br />cular fiberglass tanks (2,200 L); two tanks con-
<br />tained treatment fish and one contained control
<br />fish. We covered the tanks with polyvinyl chloride
<br />mesh to prevent the escape of fish and with black
<br />plastic sheets to reduce the light. Striped bass were
<br />allowed about 2 weeks to recover from the anes-
<br />thetic and acclimate further to confinement before
<br />the experiment was begun.
<br />Each tank was aerated and received a continu-
<br />ous flow (about 250 LIb) of well water. Water
<br />temperature (20oC) was controlled separately in
<br />each tank and was measured daily. Well-water
<br />quality during the test period was pH, 6.9; alka-
<br />linity, 33 mg/L (as CacoJ); hardness, 30 mg/L (as
<br />CacoJ); conductivity, 99 JLS/cm; total dissolved
<br />solids, 85 mg/L; nitrite plus nitrate, 0.22 mg/L;
<br />and ammonia, 0.06 mg/L.
<br />Selenium-contaminated red shiners were seined
<br />weekly from Belews Lake (Figure 1, C) with a
<br />6-mm-square-mes~ net. The fish (weighing about
<br />1 g each) were maintained in tanks of aerated Be-
<br />
<br />401
<br />
<br />lews Lake water in the laboratory. A large supply
<br />of uncontaminated red shiners. was unavailable;
<br />therefore, uncontaminated golden shiners (about
<br />I g each) were used as a comparison diet. Golden
<br />shiners were obtained biweekly, via a local bait
<br />dealer, from Anderson Minnow Farm, Lonoke,
<br />Arkansas, and maintained in a tank of aerated well
<br />water. The percentage of protein, fat, ash, and
<br />moisture content was determined for two com-
<br />posite whole-body samples of each prey fish.
<br />Analyses were performed at Lancaster Laborato-
<br />ries, Lancaster, Pennsylvania, and followed AOAC
<br />(I 984) methods.
<br />During the experiment, all striped bass were fed
<br />to satiation three times per week. Preweighed ra-
<br />tions ofIive red shiners, blotted to remove excess
<br />moisture, were added to the two treatment tanks.
<br />Similarly prepared rations of live golden shiners
<br />were added to the control tank. Striped bass were
<br />allowed 5 h to feed. During feeding, ,he tank cov-
<br />ers were removed, laboratory lights were dimmed,
<br />and fish behavior was observed from behind black
<br />plastic curtains. At the end of each feeding session,
<br />uneaten prey was removed, blotted, and weighed.
<br />The average weight of food consumed per striped
<br />bass in a tank was calculated by' subtracting the
<br />weight of surviving prey after each feeding session
<br />from the weight initially provided, and then di-
<br />viding this difference by the number of striped
<br />bass present. The average amount of selenium in-
<br />gested per striped bass in a tank was calculated by
<br />multiplying the mean prey consumption by the
<br />measured whole-body selenium concentration in
<br />the prey.
<br />Composite whole-body samples of each prey fish
<br />were collected (days 4, 4, 35, and 77 for golden
<br />shiners; days 4,4, 10, 19, 35,43,66, 77, and 80
<br />for red shiners) for neutron activation analysis for
<br />selenium at the Department of Nuclear Engineer-
<br />ing, North Carolina State University, Raleigh. Ir-
<br />radiation and counting parameters have been re-
<br />ported previously (Finley 1985). One lot of red
<br />shiners was sampled 1, 5, and 7 d after arrival in
<br />the laboratory to estimate depuration of selenium
<br />from the fish during the holding period.
<br />Early in the study, characteristic changes in be-
<br />havior were observed 1 or 2 d before death for
<br />striped bass fed selenium-laden red shiners.
<br />Thereafter, moribund striped bass exhibiting these
<br />changes were killed by an overdose of anesthetic,
<br />weighed, and measured. A sample of epaxial skel-
<br />etal muscle was taken for neutron activation anal-
<br />ysis for selenium. Samples of liver and trunk
<br />kidney were dissected, cut into approximately 0.5-
<br />
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