EFFECT OF DIETARY SELENIUM ON THE REPRODUCTIVE SUCCESS OF BLUEGILLS (LEPOMIS-MACROCHIRUS)

The effects of dietary and waterborne selenium on the reproductive success of adult blue-gills were evaluated in a chronic toxicity study. Before spawning, two-year-old bluegills were exposed for 60 d to six combinations of dietary and waterborne selenium. Mean seleno-L-Methionine (as selenium) concentrations measured in the diet were 0.8 (control), 4.6, 8.5, 16.8, and 33.3 mug/g (dry weight). Waterborne selenium was supplied as a 6:1 mixture of selenate and selenite. Nominal waterborne selenium exposure concentration was 10 mug/L in all exposures except the control. Morphological measurements of adult fish, including length, weight, condition factor, and Gonado Somatic Index, were measured at days 60 and 140 of exposure. Reproductive indicators, including spawning frequency, number of eggs per spawn, percentage of hatch, and survival of resulting fry for 30 d after hatch were monitored during the 11-week spawning period. Selenium concentrations were determined in adult fish, eggs, and 30-d-old fry. Only fry were significantly affected. Survival was severely reduced in fry of parents exposed to 10 mug/L waterborne selenium in combination with dietary exposure of 33.3 mug/g (dry weight) seleno-L-methionine. These results support field observations that indicate food-chain accumulation of selenium can severely reduce reproductive success of bluegills.