THE INFLUENCE OF HIGH ORAL DOSES OF MERCURIC-CHLORIDE ON ORGAN TOXICANT CONCENTRATIONS AND HISTOPATHOLOGY IN RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

1. Trout were fed a pellet diet for 42 d contaminated with mercuric chloride to provide a mercury concentration of 10 g metal/kg dry weight of food. 2. Sloughing of the gut epithelium and food regurgitation occurred in the last 3 weeks of the study, but no mortalities were observed. 3. The kidney showed increased numbers of melano-macrophages, but gill pathology was notably absent. 4. Mercury accumulated in the gill, liver, kidney, muscle and mucus. The highest toxicant concentrations were recorded in the gill and liver, while contamination in the muscle was lower than most tissues examined. 5. Fish excreted mercury via the body surface mucus, a previously unknown route of mercury clearance. Mucus mercury content correlated positively with whole body burdens, suggesting mucus toxicant levels may be used to identify mercury contamination in live fish.