ACQUIRED RECOGNITION OF CHEMICAL STIMULI FROM PIKE, ESOX-LUCIUS, BY BROOK STICKLEBACKS, CULAEA INCONSTANS (OSTEICHTHYES, GASTEROSTEIDAE)

In this study we test whether brook sticklebacks (Culaea inconstans) c an acquire predator recognition through releaser-induced recognition l earning, i.e, simultaneous exposure to aversive ('releasing') stimuli and neutral stimuli causing learned aversion to the neutral stimuli. W e exposed wild-caught pike-naive brook sticklebacks (collected from a creek containing fathead minnows, Pimephales promelas, but not pike, E sox lucius) to chemical stimuli from pike that were mixed with brook s tickleback skin extract, fathead minnow skin extract, or a control of distilled water. In subsequent tests 2d later, when only pike stimuli were presented, sticklebacks conditioned with stickleback skin extract and fathead minnow skin extract exhibited antipredator behaviour (i.e . increased schooling and movement toward the substrate), while those conditioned with distilled water did not. Sticklebacks conditioned wit h stickleback skin extract responded to pike with a more intense respo nse, in terms of movement toward the substrate, than those conditioned with fathead minnow skin extract, suggesting that conspecific skin ex tract may be a stronger stimulus than heterospecific skin extract for learning recognition of predators. To our knowledge this is the first study to demonstrate that an acanthopterygian fish can acquire predato r recognition through the pairing of conspecific alarm pheromone with the cue of a predator. Furthermore, our results are the first to demon strate that fish can acquire predator recognition through the pairing of a heterospecific alarm pheromone with the cue of a predator. These results suggest that brook sticklebacks will benefit by being in close proximity to fathead minnows. Acquired predator recognition has long- term consequences in mediating predator-prey interactions.