FOOD-HABITS OF ESTUARINE STAGHORN SCULPIN, LEPTOCOTTUS-ARMATUS, WITH FOCUS ON CONSUMPTION OF JUVENILE DUNGENESS CRAB, CANCER-MAGISTER

The impact of predation by staghorn sculpin, Leptocottus armatus, on n ewly settled Dungeness crab, Cancer magister, in the Washington coasta l estuary of Grays Harbor was studied. Staghorn sculpin are known to b e generalist, opportunistic feeders, with relatively high food require ments for estuarine growth during warm summer months. During late spri ng or early summer, vast numbers of crab megalopae reach the estuary a nd settle on intertidal flats and in subtidal channels. During the nex t two months the young-of-the-year (0+) crab population is rapidly red uced by predation, including cannibalism. Crab without appropriate ref uge habitat are highly vulnerable to predation by fish, and accordingl y survival of young crab is highest in intertidal shell and eelgrass b eds. Abundance and summer growth of crab and sculpin within the estuar y were documented by monthly trawling surveys (April to August) in 198 9. Stomach contents of sculpin were analyzed to characterize the overa ll summer diet, to note monthly shifts in major prey items within two age classes of sculpin (0+ and 1+), and to contrast sculpin prey consu med in eelgrass with that consumed in shell habitats. The predominant prey species varied across the categories above but generally included ghost and blue mud shrimp, Neotrypaea californiensis and Upogebia pug ettensis, a nereid polychaete (Nereis brandti), juvenile Dungeness cra b, Cancer magister, and sand shrimp (Crangon spp.). Some combination o f these species composed 85% of the total diet (on the basis of percen tage of total Index of Relative Importance; %IRI) across time and betw een habitats. A comparison of diets of sculpin collected at eelgrass a nd shell habitats was significantly different; a strong preponderence of 0+ crab were consumed at the shell habitat. Nereis brandti was the most important prey for 0+ sculpin, whereas Neotrypaea californiensis was the most important for 1+ and older sculpin. The importance of she ll as refuge habitat for C. magister and the apparent contradiction in the observation that a large number of 0+ crab were taken by sculpin at the shell habitat are discussed.