Effects of Coarse Woody Habitat Complexity on Predator-Prey Interactions of Four Freshwater Fish Species

Prey refuges are an important mechanism by which habitat structure affects ecological communities. In freshwater fish communities, most research has focused on aquatic vegetation and neglected alternative habitats. We explored the interactions between predator foraging modes of two common littoral piscivores (Muskellunge Esox masquinongy and Largemouth Bass Micropterus salmoides), and antipredator behaviors of two common prey species (Golden Shiner Notemigonus crysoleucas and Bluegill Lepomis macrochirus) across a gradient of coarse woody habitat (CWH) complexity in a mesocosm setting. We hypothesized that experiments employing a generalist predator (Largemouth Bass) and behaviorally flexible prey (Bluegills) would show a stronger refuging effect of CWH than would a less gbehaviorally flexible prey (Golden Shiners) and an obligate ambush predator (Muskellunge). Predator-prey interactions were observed in laboratory pools containing coniferous deadfalls. A refuging effect of coarse wood was not supported under our experimental conditions. Golden Shiners experienced an increase in mortality rate with increasing coarse wood complexity when preyed upon by Largemouth Bass. Both prey species reduced activity rates with increasing CWH complexity when preyed upon by Largemouth Bass but exhibited different response patterns for changes in shoal size, number of isolated individuals, and proximity to predators, which may explain differences in vulnerability across the habitat gradient. Increasing CWH complexity was associated with changes in Largemouth Bass behaviors, including reductions in activity rates and reduced capture efficiency at intermediate complexities, but the changes depended on the prey species. Habitat complexity did not strongly affect foraging success or behavior of Muskellunge. Our results reinforce the importance of species-specific behavioral traits in determining influences of physical habitat on predator-prey relationships in freshwater fish communities.