Effects of Turbidity on Foraging of Black and White Crappie

Growth during early ontogeny is an important predictor of survival to recruitment for many fish species. Relatedly, growth during the juvenile stage is often influenced largely by foraging behaviors, which change in response to prey availability and environmental influences. Black crappie and white crappie are two prominent freshwater sportfish species with highly variable recruitment, for which an explanation remains largely undefined. Turbidity has been identified as one potential factor affecting crappie growth and survival, yet the mechanisms driving this effect are unclear. To explore these mechanisms, juvenile (20-80mm TL) black crappies and white crappies were fed a diet of Daphnia at a range of naturally-occurring levels of turbidity (0-50 NTU) and prey sizes (0.8-2.6mm), at both high (25/L) and low (2.5/L) prey densities. Diet counts and prey size selectivity were analyzed for each species and compared. Black crappie consumed more prey and foraged more selectively when turbidity and prey density were highest. White crappie showed little change in number of prey consumed among treatments, but captured consistently fewer and larger prey items than black crappie. These results indicate that turbidity does not seem to restrict foraging efficiency of juvenile crappies, but may affect recruitment through more complex interactions.