THE INFLUENCE OF PREDATOR PRESENCE ON UTILIZATION OF ARTIFICIAL SEAGRASS HABITATS BY JUVENILE WALLEYE POLLOCK, THERAGRA-CHALCOGRAMMA

Behavioral preference for a structured habitat (artificial seagrass) b y juvenile walleye pollock, Theragra chalcogramma, was tested in contr olled laboratory experiments. We monitored position of fish in 2000 1 tanks with and without artificial seagrass present in one half of the tank. In addition, we exposed walleye pollock to a predator model, ass essing their response when a grass plot was available or unavailable a s a potential refuge. In the absence of predators, the fish avoided th e artificial seagrass, displaying a preference for the open water side of the experimental tanks. In the presence of a predator model, howev er, juvenile walleye pollock readily entered the artificial seagrass p lots. In addition, they often remained in the grass canopy in proximit y to the predator instead of moving out of the grass to avoid the pred ator (when no grass was present they consistently moved to the opposit e side of the tank from the predator). The behavioral choices exhibite d in this study suggest that juvenile walleye pollock modify habitat s election in response to perceived predation risk, and recognize the st ructure provided by artificial seagrass as a potential refuge.