Reference 13124

The impact of predation by staghorn sculpin, Leptocottus armatus, on newly settled Dungeness crab, Cancer magister, in the Washington coastal estuary of Grays Harbor was studied.Staghorn sculpin are known to be generalist, opportunistic feeders, with relatively high food requirements for estuarine growth during warm summer months.During late spring or early summer, vast numbers of crab megalopae reach the estuary and settle on intertidal flats and in subtidal channels.During the next two months the young-of-the-year (0+) crab population is rapidly reduced by predation, including cannibalism.Crab without appropriate refuge habitat are highly vulnerable to predation by fish, and accordingly survival of young crab is highest in intertidal shell and eelgrass beds.Abundance and summer growth of crab and sculpin within the estuary were documented by monthly trawling surveys (April to August) in 1989.Stomach contents of sculpin were analyzed to characterize the overall summer diet, to note monthly shifts in major prey items within two age classes of sculpin (0+ and 1+), and to contrast sculpin prey consumed 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 pugettensis, a nereid polychaete (Nereis brandti), juvenile Dungeness crab, Cancer magister, and sand shrimp (Crangon spp.).Some combination of these species composed 85% of the total diet (on the basis of percentage of total Index of Relative Importance; %IRI) across time and between habitats.A comparison of diets of sculpin collected at eelgrass and shell habitats was significantly different; a strong preponderance 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 shell 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.