Importance of Gamete Losses in Measurements of Freshwater Fish Production

Changes in teh maturity, weight and chemistry of ovaries of bluegills, Leopomis macrochirus, taken from Pewaukee Lake, Wisconsin, were observed during the summer of 1963. In June all ovaries were either in spawning condition or very close to this stage; by September all were completely spent. Between June and September the average ovary of an age—group—II female decreased in wet weight from 8.7 to 1.9 g, a decrease of 6.8 g (2.5 g dry weight). Protein accounted for 1.7 g of the decrease in dry weight whereas fat accounted for about 0.7 g. These losses are comapred with the body weight of the fish and annual growth by individuals. Protein loss as spent ova was calculated to be about 13% of the total somatic protein of a spawning female and about 24% of the somatic protein gained by the fish as annual growth during the previous year. The substantial losses of protein as spent gametes are discussed relative to estimates of production by freshwater fish populations.