Hatcheries are effective at producing large numbers of fish for augmenting fisheries or conserving endangered populations, but the fish they produce are often predator-naive, resulting in high levels of predation mortality when the fish are first released into natural water bodies. Fish normally acquire recognition of novel stimuli as indicators of danger when injury-released chemical cues from conspecifics (a known indicator of an actively foraging predator) are presented simultaneously with a novel stimulus (e.g., predator odor, image). Thus, fish in wild populations quickly learn the sight and smell of their predators. Past research has demonstrated that predator-naive, hatchery-reared fish can be trained to recognize predators and that fish trained by this method have a significantly greater probability of surviving an encounter with a predator. To implement predator training in fishery management, predator recognition training must be feasible on a large scale in a way that does not place an undue financial or logistical burden on fisheries managers. Here, we demonstrate that groups of fish can be quickly and easily conditioned to recognize the odor of a novel predator and react to it with antipredator behavior. This simple method could improve the cost effectiveness of any stocking program, result in greater densities of managed stocks, and enhance the direct and indirect economic benefits of a fishery.Effective antipredator behavior is a major determinant of cohort survival. The first step in any antipredator response is recognition of predation risk (Lima and Dill 1990;Smith 1992). Antipredator response to chemical cues released by injured conspecifics is a widespread phenomenon among aquatic animals, ranging from ciliates to amphibians (see Wisenden 2003 for a review) because these cues are reliably released in the context of predation. Recognition of predators and correlates of predation risk by fish is often mediated directly or indirectly by chemical