Effects of turbidity and habitat complexity on the foraging behavior of the black bullhead (<i>Ameiurus melas</i>)

The role of vertebrate scavengers in nutrient flow of aquatic ecosystems has recently been emphasized. Evidence is accumulating that scavenging is an alternative tactic for certain predatory fish, but their foraging choices between scavenging and predation under varying environmental conditions have not been studied. In this study, we presented black bullheads, Ameiurus melas (Rafinesque, 1820), with both live and carcass prey of tubenose gobies, Proterorhinus semilunaris (Heckel, 1837), in aquaria with varying levels of turbidity and habitat complexity. Our findings revealed that black bullheads exhibit higher consumption of carcass prey in complex habitat and clear water conditions. We also provide evidence of the active predatory behavior displayed by black bullheads; a greater consumption of live prey was observed in simple habitat and turbid water. We found no relationship between individual exploratory behavior and the choice between carcass and live prey in black bullheads. Our results suggest that the choice between scavenging versus predatory foraging strategy under varying environmental conditions is influenced by the behavior of both consumer and prey. The ability of black bullheads to adapt their foraging strategy in different environments may contribute to their widespread success as an invasive species.近年来，脊椎动物食腐者在水生生态系统养分循环中的作用日益受到学界重视。越来越多的证据表明，食腐行为是部分掠食性鱼类的替代觅食策略，但目前尚无研究探讨此类鱼类在不同环境条件下于食腐与捕食之间的觅食选择偏好。本研究以斑真鮰（Ameiurus melas, Rafinesque, 1820）为受试对象，在浊度与生境复杂度各异的水族箱中，为其提供活体及尸体制备的突吻虾虎鱼（Proterorhinus semilunaris, Heckel, 1837）作为猎物。研究结果显示，斑真鮰在复杂生境与清水条件下对腐尸猎物的摄食率更高。本研究同时证实了斑真鮰存在主动捕食行为：在简单生境与浊水环境中，其对活体猎物的摄食量显著更高。本研究未发现斑真鮰的个体探索行为与其在腐尸与活体猎物间的觅食选择存在关联。研究结果表明，在不同环境条件下，食腐与捕食两种觅食策略的选择会受到捕食者与猎物双方行为的共同影响。斑真鮰在不同环境中调整觅食策略的能力，或为其作为入侵物种的广泛成功提供了助力。