Effects of Predator-Prey Interactions and Benthic Habitat Complexity on Selectivity of a Foraging Generalist

Predators typically prefer specific prey types but include others in their diet as a result of opportunistic foraging, prey availability, or foraging costs. Habitat complexity may interact with preferences by altering prey availability and foraging strategies, affecting the preferences and consumption patterns of predators. Yellow perch Perca flavescens is perceived as a foraging generalist and the predominant predator in numerous systems. In the laboratory, we compared the prey selection of yellow perch (230-311 mm) foraging on common Great Lakes prey species-northern crayfish Orconectes virilis, round gobies Neogobius melanostomus, and alewives Alosa pseudoharengus-in simple and complex benthic habitats. Yellow perch selected alewives in both simple and complex habitats. Removal of the preferred prey species resulted in neutral selection for both of the remaining prey species in simple benthic habitat but selection for round gobies and against crayfish in complex habitat. Predator behaviors indicated that alewives were captured efficiently and easily handled whereas round gobies and crayfish were not. The diets of yellow perch in Lake Michigan reflected patterns established in mesocosm experiments. Although prey species were probably not equally abundant in the natural environment, alewives comprised the greatest biomass in yellow perch diets, followed by round gobies and crayfish. Our results indicate that predators typically considered as generalist foragers can have prey preferences and rely heavily on a single prey species as a result of differences in prey vulnerability, profitability, and habitat complexity.