Behavioral Response of Blacknose Dace (Rhinichthys atratulus) to Varying Densities of Predatory Creek Chub (Semotilus atromaculatus)

We investigated the behavioral response of juvenile blacknose dace (Rhinichthys atratulus) to varying levels of predation risk by varying the density of predatory creek chub (Semotilus atromaculatus) and amount of structure in compartments of an artificial field stream. When structure in predator locations was low, dace did not avoid predators during the day but did at night, responding equally regardless of predator density. When structure was increased, the strength of avoidance at night was dependent on both the amount of structure and density of predators. Predators in experimental compartments caused dace to move to other locations of the stream. By moving away from predators, dace gain a short-term benefit in avoiding predation and a long-term benefit by reducing the chance of becoming trapped in pools with piscivorous fish when water levels in a natural stream drop. However, this shift could reduce feeding if dace move to locations poor for foraging or high in density of dace.