EFFECTS OF ZINC ON JUVENILE ATLANTIC SALMON SALMO-SALAR - ACUTE TOXICITY, FOOD-INTAKE, GROWTH AND BIOACCUMULATION

The effects of long-term zinc exposure on juvenile salmon were assessed by measuring changes in their voluntary food intake, growth and rate of zinc accumulation. The food intake of salmon surviving concentrations as great as the 21-day LC50 was initially reduced but returned to amounts observed for control fish within 10 to 20 days. After 45 days' exposure, the food intake of these individuals was greater than that of the controls. Growth rates of salmon exposed to zinc (maximum concentration estimated to cause mortality ≤50% during an acute bioassay) and offered rations of 2.0 or 3.5% dry body weight per day were not reduced during a three-month period. However, caloric content of salmon at the higher concentrations showed a small decrease during the experimental period. Zinc concentration of salmon feeding to satiation once daily and exposed to zinc increased during the first two months of exposure before reaching a maximum, while zinc concentration of salmon offered sub-excess rations (2.0 and 3.5% per day) increased linearly during a three-month period. © 1979.