Conflicting natural and anthropogenic threats reduce nest success in centrarchid fishes

Abstract

As anthropogenic presence in riverine systems increases, it is essential to understand the associated impacts on ecologically important species such as centrarchid fishes. We tested the hypothesis that the conflicting pressures of natural factors (e.g., predation threat), the perceived threat of human traffic, and the impacts of habitat degradation would negatively influence centrarchid nest success. We surveyed centrarchid nesting areas in the Cacapon River, West Virginia, USA and collected a suite of biotic and habitat variables for each nest found. From these data, we analyzed site selection and nest success in three centrarchid species and male flight response to perceived harm in the most common (longear sunfish, Lepomis megalotis). We detected patterns of nest site selection in all species surveyed, with a large degree of overlap in influential variables. Males did not select for nest sites near in-stream cover, which appeared to reduce nest success by acting as refugia for benthic brood predators. However, the protection provided by cover dampened the magnitude of response to perceived harm. Therefore, the pressures of human and natural threats were contradictory, likely reducing fitness and fecundity. Future restoration procedures should seek to conserve nesting habitat by limiting the impacts of human presence.