The influence of hypoxia on risk of predation and habitat choice by the fathead minnow, Pimephales promelas

Abstract.

Yellow perch (Perca flavescens) have a lower physiological tolerance to hypoxic environments than one of its prey species, the fathead minnow (Pimephales promelas). These data suggest that environments where dissolved oxygen concentration is lethal to perch, but not fathead minnows, could provide a predator-free refuge. Here, we test the hypothesis that differences in tolerance to hypoxic environments need not be lethal to provide more tolerant prey species with an environment that has a significantly reduced or eliminated predation risk. We predict that moderate hypoxic environments will generate non-lethal stress in predators, rendering them ineffective at capturing their prey. For this hypothesis to operate, we assume that prey are capable of detecting when their predators are stressed and less of a threat, and discount the risk of predation associated with these predators. Fathead minnows were provided with the option of feeding in relatively low- versus high-risk locations or in the presence of a yellow perch under sub-lethal hypoxic and normoxic conditions. Fathead minnows exhibited a significantly reduced response to the predator in hypoxic conditions relative to normoxic conditions. We also observed significant variation in the behaviour of the predator under these two conditions which may provide the cue used by prey to discount the threat associated with the predator.