The assessment of episodic metal pollution. II. The effects of cadmium and copper enriched diets on tissue contaminant analysis in rainbow trout (Oncorhynchus mykiss).

Rainbow trout, Oncorhynchus mykiss, were fed on a commercial feed enriched with either Cd or Cu for 32 days and allowed to recover on normal food for 12 days. The body burden of fish fed Cd-enriched diet increased from about 0.05 to 0.39 micrograms/g wet weight, reflected by elevation in the Cd content of gill, liver, blood plasma, kidney, skin, mucus, and whole gut. Muscle Cd content did not alter. Most organs remained contaminated with Cd after 12 days depuration. The body burden of animals fed Cu-enriched diet increased from about 1.2 to 1.5 micrograms/g wet weight, with the gill, whole gut, blood plasma, skin, and mucus contaminated after 32 days, no changes in the liver and muscle occurred. All organs, except the gill and kidney, returned to control values after 12 days depuration. In exposed animals, 76 and 53% of the Cd or Cu body burden, respectively, were contained in the gut, unlike waterborne exposure. Differences in the body distribution of toxicants after intermittent waterborne and dietary exposure may identify the principal routes of pollutant uptake. Ratios of toxicant concentrations in gill/liver may establish the exposure status of fish, but cannot be used to differentiate dietary and waterborne contamination. Analysis of mucus may identify waterborne Cu exposure; dietary and waterborne contributions to mucus Cd content are more difficult to establish.