Abstract. — The impact of preop- 

 tion by staghorn sculpin, Leptocottus 

 armatus, on newly settled Dungeness 

 crab, Cancer magister, in the Washing- 

 ton coastal estuary of Grays Harbor 

 was studied. Staghorn sculpin are 

 known to be generalist, opportunistic 

 feeders, with relatively high food re- 

 quirements for estuarine growth dur- 

 ing 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 pre- 

 dation, 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 eel- 

 grass 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 in- 

 cluded 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 com- 

 parison of diets of sculpin collected at ee- 

 lgrass and shell habitats was signifi- 

 cantly 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 shell as refuge habitat for 

 C. magister and the apparent contradic- 

 tion in the observation that a large num- 

 ber of 0+ crab were taken by sculpin at 

 the shell habitat are discussed. 



Food habits of estuarine staghorn 

 sculpin, Leptocottus armatus, 

 with focus on consumption of 

 juvenile Dungeness crab, 

 Cancer magister* 



Janet L. Armstrong 

 David A. Armstrong 

 Stephen B. Mathews 



School of Fisheries. WH-1 



University of Washington, Seattle, Washington 98195 



Manuscript accepted 23 November 1994. 

 Fishery Bulletin 93:456-470 (1995). 



Staghorn sculpin, Leptocottus arma- 

 tus, are common in major estuaries 

 throughout their range from Baja 

 California through the Gulf of Alaska 

 (Hart, 1974). Young sculpin inhabit 

 brackish water streams and chan- 

 nels and move down into the estu- 

 ary as they grow larger during their 

 first year. Older juvenile and adult 

 sculpin are broadly distributed 

 throughout estuarine nursery areas 

 utilized by juvenile crab and are 

 known predators of Dungeness 

 crab, Cancer magister, within estu- 

 aries (Reilly, 1983). Staghorn scul- 

 pin have wide gapes and relatively 

 large mouth areas in relation to 

 their size compared with other spe- 

 cies of fish predators commonly 

 found in estuaries during the sum- 

 mer. 1,2 They are opportunistic, gen- 

 eralist predators (Jones, 1962; Hart, 

 1974; Birtwell et al., 1984) and feed 

 heavily on decapod crustaceans 

 such as the yellow shore crab, 

 Hemigrapsus oregonensis, the ghost 

 shrimp Neotrypaea californiensis, 

 and pea crab, Pinnixa sp. (Tasto, 

 1975; Posey, 1986). Staghorn scul- 

 pin are described as visual preda- 

 tors that move onto estuarine 

 tideflats with the incoming tide 

 (Tasto, 1975); their foraging behav- 

 ior may contribute to the high mor- 

 tality rate of small 0+ crab (Wain- 

 wright et al., 1992). 



The Grays Harbor estuary, Wash- 

 ington, contains extensive intertidal 

 tracts of eelgrass and shell that 

 serve as critical nursery areas for 

 young-of-the-year (0+) and one- 

 year-old (1 + ) Dungeness crab 3 

 (Gutermuth and Armstrong, 1989; 

 Gunderson et al., 1990; Jamieson 

 and Armstrong, 1991). During high 

 tides in May and June, vast num- 

 bers of crab megalopae reach estu- 

 aries, settle to the benthos, and 

 metamorphose to the first juvenile 

 instar (Jl). Crab settle over broad 

 expanses of the intertidal sandflats 



Contribution 903 of the University of 

 Washington, School of Fisheries, Seattle, 

 WA 98195. 



1 Smith, J. L. 1976. Impact of dredging on 

 the fishes in Grays Harbor. Appendix G in 

 Maintenance dredging and the environ- 

 ment of Grays Harbor, Washington. Final 

 Rep. by U.S. Army Corps of Engineers, 

 Seattle District, 94 p. 



2 McGraw, K., and D. A. Armstrong. 1990. 

 Fish entrainment by dredges in Grays Har- 

 bor, Washington. In C. A. Simenstad (ed.), 

 Effects of dredging on anadromous Pacific 

 coast fishes; workshop proceedings, Se- 

 attle, WA, 8-9 Sep. 1988. Washington Sea 

 Grant Program, Univ. Washington, Se- 

 attle, WA 98195, 160 p. 



3 Armstrong, D. A., T. C. Wainwright, J. M. 

 Orensanz, P. A. Dinnel, and B. R. Dum- 

 bauld. 1987. Model of dredging impact on 

 Dungeness crab in Grays Harbor, Wash- 

 ington, Final Rep. FRI-UW-8702 to Bat- 

 telle Northwest Laboratories and U.S. 

 Army Corps of Engineers, Seattle, District, 

 Seattle, WA, 167 p. 



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