Juvenile Lake Sturgeon Go To School: Life-Skills Training for Hatchery Fish

Hatchery supplementation of declining fish populations is commonly employed to try to increase year-class strength. However, the success of such programs is often hampered from low postrelease survival as a result of the failure of hatchery fish to appropriately recognize predation threats. Not surprisingly, there has been considerable effort to train prey to recognize predators prior to release. The objective of our current work was to characterize the antipredator response of hatchery-reared, predator-naive young-of-the-year Lake Sturgeon Acipenser fulvescens (an endangered species) to alarm cues from injured conspecifics and test whether these alarm cues could be used to train sturgeon to recognize unknown predators. We found that skin-derived alarm cues elicited an antipredator response without learning and that learning required cues coming from whole-body grinds, presumably because they represent a much more reliable indicator of risk. When the experiment was repeated with older sturgeon from Wolf River (Wisconsin), training with cues from whole-body grinds did not enhance the response. Subjecting the fish to several training sessions (six over 3 d) led to some alteration in behavior. Our results provide insights into how ontogenetic changes (size, scute growth) could explain the different learning outcomes from the larger fish as related to hatcheries and conservation programs.