Effect of predation and habitat quality on growth and reproduction of a stream fish

Anthropogenic disturbances are rarely independent, requiring native fishes to respond to multiple factors to persist in changing environments. We examined the interaction of predation environment (presence of introduced brown trout, Salmo trutta) and habitat quality on growth and reproduction of southern leatherside chub, Lepidomeda aliciae, a small-bodied stream fish native to central Utah, USA. Southern leatherside chub were sampled from four streams representing a complete two-factor cross of predation environment and habitat quality. Growth was estimated using increment analysis of annuli on otoliths, and reproductive traits were measured for both sexes. Southern leatherside chub growth was greater in high-quality than in low-quality habitats, and greater in predator than in nonpredator environments. However, fish exhibited a greater growth response to presence of brown trout in low-quality habitats. Southern leatherside chub growth followed predictions of plastic responses to resource availability based on habitat quality and predation environment (lethal vs. nonlethal effects). Reproductive allocation (gonad wet mass) was significantly greater in low-quality versus high-quality habitats, but was unaffected by predation environment. Other female life-history traits were affected either by both effects or their interaction. Reproductive responses to habitat quality and predation environment were consistent with predictions based on differential mortality. Southern leatherside chub growth and reproduction responded differently to the combination of habitat quality and predation environment, thus demonstrating the importance of assessing interacting effects of anthropogenic disturbances to more fully comprehend impacts on native species and to appropriately manage, recover and restore these species and their habitats.