A Laboratory Evaluation of Poststocking Predatory Losses for Cultured Largemouth Bass

Abstract

Stocking fish into preexisting fish communities is not always successful. Although there may be many reasons why stockings fail, predation is perhaps the most likely reason. Reducing predation by allowing fish to become accustomed to their new environment before release (i.e., habituation) may improve stocking efficiency. We evaluated the effect of habituation on predation of stocked, hatchery-reared fingerling Florida largemouth bass Micropterus salmoides floridanus (30–64 mm total length) in simple (i.e., open-water) and structurally complex (i.e., with vegetation and cobble) habitats in indoor tanks. We found that fingerling largemouth bass survival significantly increased (P < 0.004) from 26% to 46% when fish were habituated in a predator-free enclosure for at least 15 min. Surviving fish spent most (95%) of their time in the structurally complex habitat. However, the survival of all fish stocked in structurally complex habitat did not differ from that of all fish stocked in open water (P = 0.61). Although predation on nonhabituated, hatchery-reared largemouth bass approached 75%, we found that short-term habituation can enhance survival of stocked largemouth bass, as manifested by improved predator avoidance. This suggests that habituating fingerling largemouth bass before stocking may result in substantial increases in survival.