An Experimental Study of Consumption of Channel Catfish Ictalurus punctatus by Largemouth Bass Micropterus salmoides when Alternative Prey Are Available

Fish spines can impede predation by gape-limited predators by increasing the difficulty and danger of swallowing, but do predators avoid dangerous prey in favor of less dangerous species in a choice situation, i.e., Forbes' “dangerous prey” hypothesis? We tested this hypothesis by giving Largemouth bass Micropterus salmoides a choice of three species with different degrees of spination: Goldfish (Carassius auratus), Bluegill sunfish (Lepomis macrochirus), and Channel catfish (Ictalurus punctatus). We hypothesized that Largemouth bass predation would be greatest for Goldfish (relatively spineless), less for Bluegills (thin, flexible, and sharp dorsal and anal spines), and least for channel catfish (stout pectoral spines that can be abducted and locked, thus increasing the effective girth of the fish). Prey fish were presented in paired combinations (Experiment 1) or with the three species together (Experiment 2) to individual Largemouth bass in net pens. Fewer Channel catfish were consumed in both experiments, whereas Goldfish and Bluegill were consumed equally. Pectoral spines of channel catfish appeared to deter predation, but Bluegill spines did not afford greater protection compared to relatively spineless Goldfish.