A Comparison of Black Carp, Redear Sunfish, and Blue Catfish as Biological Controls of Snail Populations

Redear sunfish Lepomis microlophus and blue catfish Ictalurus furcatus were compared with black carp Mylopharyngodon piceus as potential biological controls for rams‐horn snails Planorbella spp. Comparisons were made with regard to snail size selection, total consumption, and the effects of alternative prey and temperature on consumption rates of two size‐classes for each species, small (≤100 mm total length [TL]) and large (>100 mm TL). Examination of stomach contents revealed that black carp and redear sunfish crush snails, whereas blue catfish do not. Electivity indices showed that large black carp randomly consumed snails from all shell lengths, whereas large redear sunfish avoided snails larger than 13 mm. Large black carp, redear sunfish, and blue catfish consumed commercial feed when provided in conjunction with snails. The largest amount of snail consumption by all fish species occurred at 26°C, and declined slightly as water temperature decreased from 26°C to 12°C. Black carp were the most effective consumers of rams‐horn snails and did not show any preference for a particular size or range of sizes of snails. Redear sunfish consumed significantly fewer snails than black carp but significantly more than blue catfish. In this study, redear sunfish were a better biological control of rams‐horn snails than blue catfish but not as effective as the exotic black carp. However, further studies need to be conducted under natural conditions to determine whether the presence of other natural prey items will affect the selectivity of redear sunfish with respect to rams‐horn snails.