Turbidity as an ecological constraint on learned predator recognition and generalization in a prey fish

The way in which prey animals respond to predators is crucial in shaping direct and indirect interactions in ecosystems. Here, we investigated how a change in turbidity would affect the ability of fathead minnows to recognize potential predators. Minnows were taught to recognize the sight of predatory brown trout and were subsequently tested for their responses to brown trout, rainbow trout or yellow perch in either clear or turbid conditions. In clear water, minnows exhibited an antipredator response towards the brown trout, but they also generalized their recognition to a novel rainbow trout. In turbid water, however, the responses of minnows towards brown trout were lessened and they did not exhibit an antipredator response to the sight of a rainbow trout. None of the minnows displayed a response upon presentation of yellow perch. These results indicate that turbidity alters the quality and quantity of visual information received by the minnows, eliminating their ability to generalize learned recognition of some predators.