THE EFFECT OF ACUTE EXPOSURE TO DIETARY CD AND CU ON ORGAN TOXICANT CONCENTRATIONS IN RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

Trout were fed on a commercial diet containing 10 g of Cd or Cu kg/dry weight of food for 28 days to determine whether fish could ingest and accumulate toxicants from heavily contaminated food. Fish initially ingested either diet, but food regurgitation eventually occurred. Dietary Cd was more toxic than Cu, causing 14 compared to one mortality. Cadmium deposition in internal organs and impaired copper metabolism contributed to mortalities in the Cd-exposed group. Dietary Cd accumulated in the gills, liver, kidney, and muscle. Oral doses of Cu appeared in the gill, liver, and muscle; but not significantly in the kidney. The highest toxicant concentrations were recorded in the gill and liver, while contamination in the muscle was lower than in other tissues examined. Only limited amounts of Cd and Cu were excreted via the body surface mucus. This study suggests that fish will ingest heavily polluted food until toxicity occurs. Wild fish may therefore be at risk from contamination via the diet after pollution incidents.