Effects of body size, gender, and prey availability on diets of snow crabs in the northern Bering Sea

In efforts to maintain or restore populations of snow crabs Chionoecetes opilio, identifying important habitats requires knowing prey preferences and availability for different sexes and life stages. We analyzed the diets of juvenile, adolescent, and adult snow crabs of both sexes relative to available prey throughout a large area of the northern Bering Sea. Snow crabs of all sizes consumed a wide variety of prey including bivalves, gastropods, polychaetes, ophiuroids, and crustaceans. The proportions of different taxa in snow crab diets corresponded closely to the relative abundance of those taxa in different areas; thus, in this region, diets of respective sexes and ages can be predicted fairly accurately from the local abundance of different prey. The only apparent differences in diet between sexes were related to the larger and stronger claws of adult males. Larger crabs consumed larger prey that required greater handling ability and claw strength, such as harder-shelled bivalves and gastropods, larger polychaetes, and other snow crabs. Juvenile crabs consumed softer, more easily manipulated prey, such as amphipods and small bivalves with thin or incompletely calcified shells. Areas of high abundance of juvenile snow crabs, previously not recognized in designating essential habitat in this region, were characterized by high abundance of amphipods and small bivalves. Quality and importance of habitat for snow crabs appeared to depend jointly on several factors: hydrographic patterns that determine locations of larval settlement and subsequent ontogenetic migration, the combined abundance of all prey taxa, and ontogenetic capabilities for handling different sizes of prey.