Experimental Evaluation of Predator‐Prey Relationships in a Patchy Environment: Consequences For Habitat Use Patterns in Minnows

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Abstract
An experimental study, using the minnows Semotilus atromaculatus and Rhinichthys atratulus, was conducted in a seminatural artificial stream to evaluate the interaction of predator presence, habitat structural complexity, and time of day in determining habitat use patterns of prey. Predators were adult S. atromaculatus, while juveniles of both species were used as prey. Prey of both species actively avoid locations in the artificial stream that contain predators. However, structural complexity and time of day each have a mediating effect on the response of the prey fish to the presence of predators. While others have shown differential survivorship of prey, dependent upon structural complexity and time of day, this study shows how prey respond behaviorally to the presence of predators in habitat patches. They are most likely to enter those patches during daylight or when structure is present. In natural headwater streams prey fish are often found in patches of high predator density where prey density is often correlated with the degree of structural complexity. Our findings offer an explanation for this variability in relative abundances of predators and prey, by relating patch use by prey habitat structural complexity and diel activity. Resulting implications for optimal foraging and guild organization are suggested.