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 (Artemi a sp.) enriched with Cu, Cd, Pb, and Zn both individually and as a mix ture combined with As. Dietary concentrations fed to trout were select ed based on metal concentrations measured in invertebrates collected f rom the Clark Fork River (CFR), Montana. In addition to dietary exposu re, treatments also included simultaneous exposure to a mixture of wat erborne metals at sublethal concentrations. Fish in all treatments sho wed increased tissue metal concentrations from water and/or dietary ex posure. Despite these accumulations, trout showed no effects on surviv al or growth from dietary concentrations as high as 55 mu g Cd/g dry w eight, 170 mu g Pb/g dry weight, or 1,500 mu g Zn/g dry weight (correc ted 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 cont ributed 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 wa s no longer present after 60 d.