Predator-recognition training enhances survival of brook trout: evidence from laboratory and field-enclosure studies

In this study we tested whether brook trout (Salvelinus fontinalis) can lea rn to recognise predators through releaser-induced recognition learning and whether this learning enhances survival of trout during encounters with a predator. In our initial experiment, we exposed hatchery-reared predator-na ive brook trout to chemical stimuli from predatory chain pickerel (Esox nig er) paired with alarm signals released by damaged trout, disturbance signal s, or distilled water. In subsequent tests 24 h later, when only pickerel o dour was presented, trout conditioned with damage-released alarm signals ex hibited antipredator behaviour (i.e., decreased movement and altered foragi ng patterns), in contrast to the other treatments, thereby demonstrating le arned recognition of the predator. In our second experiment we showed that trout retained the ability to recognise the predator for at least 10 days. In the next series of experiments we explicitly tested whether training tro ut to recognise predators confers a survival benefit. During staged encount ers with chain pickerel (in both the laboratory and the field), trained fis h were better able to evade the predator than nontrained fish. Ours is the first study to demonstrate that fish trained to recognise predators gain a survival benefit during staged encounters with a predator.