Chemosensory assessment of predation risk by slimy sculpins (Cottus cognatus): responses to alarm, disturbance, and predator cues.

Slimy sculpins (Cottus cognatus) are small benthic fish that commonly co-occur with predatory fishes throughout most of their range in North America. In two laboratory experiments we examined the nature and extent of responses of slimy sculpins to chemosensory cues from predatory brook trout (Salvelinus fontinalis) and chemical alarm cues released by conspecific sculpins. Sculpins responded to three different classes of chemical stimuli: (1) cues of predatory brook trout, (2) damage-released alarm cues from conspecific sculpins, and (3) disturbance cues from conspecific sculpins. Sculpins did not distinguish between trout fed different diets; however, the presence of damage-released alarm cues did enhance the intensity of response to the predator chemicals. A histological analysis of the skin of sculpins revealed the presence of large sacciform cells that may act as the source of chemical alarm signals.