Day-to-day variation in food consumption by Largemouth Bass

Substantial day-to-day variation in food consumption by groups of laboratory-held age-0 large mouth bass Micropterus salmoides occurred at temperatures of 14, 20, and 26 C for 108-113- and 136-140-mm size classes of fish. The largemouth bass were continuously provided with an unrestricted ration of live fathead minnows Pimephales promelas. Day-to-day differences in food consumption could not be distinguished from random variation about a mean value, indicating that day-to-day consumption levels were independent of each other. The effects of fish sample size on the number of sample dates needed to assure certain levels of precision in the estimation of mean diel food consumption over 5-week intervals (based on the feeding schedule of age-0 largemouth bass in the present study) were simulated by computer. A 95% probability of only a 10% relative error level (coefficient of variation) would require sampling 25 fish from two to four times over the 5-week period. Caution should be exercised when observed differences in food consumption by fish measured at discrete points in time are attributed to abiotic or biotic environmental factors such as differences in prey density.