Feeding Ecology of Young White Crappie in a Kansas Reservoir

Abstract

White crappie (Pomoxis annularis) are a valuable sport fish, but they have received little ecological study. They are piscivorous when large (greater than 16-17 cm TL) but are almost completely planktivorous when small. We studied the location and periodicity of crappie feeding in a series of midwater trawl studies in a Kansas reservoir and found crappie between 8 and 17 cm long to be wholly pelagic. Crappie were distributed throughout most depths during the cool times of the year but were grouped more vertically during the warmer months-in part because of the anaerobic hypolimnion extending up to the 5-m depth. Crappie rarely fed at night and fed entirely on zooplankton during the day. Daphnia, even when relatively sparse, made up much of the diet whereas diaptomid copepods were relatively rare. Feeding rates of crappie ranged from 20 to 200 prey per hour when preying on zooplankton during the morning. These rates were estimated to provide sufficient energy for small crappie (5-20 g) but only marginal energy for larger fish. The larger crappie seemed to reduce energy expenditure by feeding in the cooler metalimnion during the day. However, all crappie spent the summer evening hours in the warmer epilimnion. The reason for this seemingly inefficient evening distribution is unknown.