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<br /> 'I <br /> .. <br /> .i <br />, ., 0' <br /> ., t~''') <br />'.-"! <br />"}j t':t <br /> f.':"" <br />;1 i-'-- <br /> j "...,..;. <br />~-j <br />:..i <br />: ., <br /> <br />; , <br /> <br />USDOI 1998) for reproductive impairment in sensitive fish, Also, the dietary concentrations <br /> <br />tested here were representative of those in potential food items of adult Colorado pikeminnow in <br /> <br />the San Juan River (whole-body fish tissue, 1.3-8.3 /lg!g; Blanchard et at 1993). <br /> <br />Seleno-DL-methionine was used because it was found to be a good model for natural forms of <br /> <br />selenium in food-chain organisms, based on bioaccumulation and toxicity studies with fish <br /> <br />(Bryson et al. 1985, Hamilton et al. 1990). The test diets were formulated by BioProducts Inc. <br /> <br />(Warrington, OR) using standard production techniques. The two selenium-fortified diets were <br /> <br />prepared by adding the desired amount of seleno-DL-methionine (C5HIIN02Se), obtained from <br /> <br />Sigma Chemical (St. Louis, MO), to the dextran binder and then thoroughly mixing the binder <br /> <br />into the normal BioDiet "Brood" dough prior to pelletization. The control diet was prepared as <br /> <br />the normal BioDiet Brood dough, but without seleno-DL-methionine added to the dextran <br /> <br />binder. The dough was extruded into 6-mrn pellets and vacuumed sealed with nitrogen in plastic <br /> <br />bags, The diets were shipped by ground transport to our laboratory. Upon arrival, duplicate <br /> <br />] O-g samples were taken from each bag of diet for total selenium analysis and the diets were <br /> <br />stored in a freezer at or below -l80C. All diets were analyzed for total selenium residues prior to <br /> <br />use in the study, <br /> <br />For the waterborne exposure component, fish were exposed to nominal selenium <br /> <br />t' concentrations of 0 or 5 /lg!L, The waterborne concentration of total selenium (5 /lg!L) was <br /> <br />... <br /> <br />"", <br /> <br />based on the current water quality Criterion Continuous Concentration of 5 /lg!L (USEP A 1987), <br /> <br />Because selenate and selenite usually occur simultaneously in surface waters (USEP A ] 987), a <br /> <br />6: I ratio of selenate:selenite in the water was used to better approximate environmental <br /> <br />conditions. This ratio is representative of that found in selenium contaminated irrigation <br /> <br />drainwater entering the Kesterson National Wildlife Refuge in California (Presser and Barnes <br /> <br />9 <br />