DIETARY AND WATERBORNE EXPOSURE OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) TO COPPER, CADMIUM, LEAD AND ZINC USING A LIVE DIET

In two 60-d exposures, rainbow trout fry were fed brine shrimp (Artemia sp.) enriched with Cu, Cd, Pb, and Zn both individually and as a mixture combined with As. Dietary concentrations fed to trout were selected based on metal concentrations measured in invertebrates collected from the Clark Fork River (CFR), Montana. In addition to dietary exposure, treatments also included simultaneous exposure to a mixture of waterborne metals at sublethal concentrations. Fish in all treatments showed increased tissue metal concentrations from water and/or dietary exposure. Despite these accumulations, trout showed no effects on survival or growth from dietary concentrations as high as 55 mu g Cd/g dry weight, 170 mu g Pb/g dry weight, or 1,500 mu g Zn/g dry weight (corrected for depuration). Dietary Cu concentrations up to 350 mu g Cu/g dry weight did not reduce survival or growth. Fish fed Cu concentrations higher than those typical of CFR invertebrates (660 and 800 mu g Cu/g dry weight; corrected for depuration) showed about 30% mortality with no effect on growth; waterborne Cu released from Artemia may have contributed to this mortality. Trout exposed to diets with a mixture of Cu, Cd, Pb, Zn, and As dose to that measured in CFR invertebrates showed tower weight than did control fish after 35 d, but this difference was no longer present after 60 d.