Effects of Turbidity on Prey Selection and Foraging Return of Adult Largemouth Bass in Reservoirs

Abstract

Previous laboratory studies have demonstrated that turbidity alters prey selection by Largemouth Bass Micropterus salmoides, but this has not been tested in the field. Laboratory studies have also suggested that daily rates of consumption by Largemouth Bass may decline as turbidity increases and that the rate of decline may differ among prey types, possibly providing a mechanism that drives the observed prey selection patterns. We conducted laboratory trials to measure daily consumption rates for Largemouth Bass when foraging on Bluegills Lepomis macrochirus and Gizzard Shad Dorosoma cepedianum; we also collected field data in three reservoir systems (Boomer, Sooner, and Guthrie lakes, Oklahoma) during 2 years to evaluate Largemouth Bass prey selection and consumption rates over a range of turbidity levels. In the laboratory trials, Largemouth Bass daily consumption rates declined with increased turbidity, but the decline was similar between the two prey types. We detected no correlations between turbidity and consumption rate (percentage of empty stomachs or mean weight of prey in stomach contents) in the field. Field-measured prey selection was highly variable among reservoirs and between sampling years, yet all but one reservoir ×× year combination had significant correlations between prey selection and turbidity, which generally followed the predictions of previous laboratory results (greater use of fish prey [especially centrarchids] and reduced use of crayfish at high levels of turbidity). However, the use of crayfish prey under low-turbidity conditions was higher than that expected based on previous laboratory trials. Further research is needed to determine which factors regulate the effects of increased turbidity on predator foraging return and to evaluate the food web implications of turbidity-related changes in the diets of top predators.

Received December 3, 2014; accepted June 25, 2015

ACKNOWLEDGMENTS

We thank P. Einsig, M. Wade, J. English, and R. Kuzmic for their help in collecting field data; C. Goad for supplying valuable input on statistical analysis procedures; and A. Echelle and J. Long for providing reviews that improved the manuscript.