Daily Feeding Rates of Bluegill (<i>Lepomis macrochirus</i>) Determined by a Refined Radioisotope Method

Abstract

The daily values of 137 Cs intake by bluegill (Lepomis macrochirus) from a small impoundment receiving low-level radioactive effluents were used to calculate the daily feeding rates of the fish. The calculations of 137 Cs intake, for a nonequilibrium state, were based on fish growth, the seasonal fluctuation of 137 Cs concentration in fish, and the temperature-elimination rate relationship. The feeding rates were obtained by dividing the daily intake of 137 Cs by the concentration of 137 Cs in the diet. The daily meal of bluegill varied from 0.8% of body weight in February to 3.2% in June with an annual mean of 1.75%. There was a positive correlation (r 2 = 0.805) between the daily meal and the daily temperature. The ecological growth efficiency was 4.2% during the period from April to October.