Effects of Turbidity and Cover on Prey Selectivity of Adult Smallmouth Bass

Environmental factors such as turbidity and habitat complexity affect many aspects of aquatic food webs, including predator-prey interactions. We examined the effects of turbidity (0, 5, 10, 20, 40 nephelometric turbidity units [NTU]) and cover (presence or absence) on prey selection by adult smallmouth bass Micropterus dolomieu (mean +/- SD = 290 +/- 41 mm total length) in laboratory pools. Individual predators were given a choice of five northern crayfish Orconectes virilis, five golden shiners Notemigonus crysoleucas (a pelagic fish), or five round goby Neogobius melanostomus (an invasive benthic fish). Smallmouth bass selected round goby at low turbidities (0 and 5 NTU) and golden shiners at the highest turbidity (40 NTU) in trials without cover. With cover, smallmouth bass increased selectivity for golden shiners, particularly at the turbidity extremes (0, 20, and 40 NTU). Northern crayfish were negatively or neutrally selected in all trials across both turbidity and cover treatments. Turbidity had a greater effect than cover on prey consumption rate, which decreased as turbidity increased. Our results suggest that turbidity and cover, two important environmental variables, can influence prey selectivity by smallmouth bass.