Armstrong et al.: Food habits of Leptocottus armatus 



463 



ha where the primary epibenthic 

 cover is allochthonous leaves, 

 branches, and bark. Initial mean crab 

 densities were almost four times 

 higher in the intertidal shell than at 

 the intertidal eelgrass site (Fig. 10; 

 9,500 crab/ha vs. 2,500 crab/ha, t- 

 test, t=2A, P=0.136). At the eelgrass 

 site, intertidal and subtidal crab den- 

 sities were comparable by mid-June 

 at about 2,500/ha. As the summer 

 progressed, 0+ crab density declined 

 in the intertidal at both the shell and 

 eelgrass sites to about 900/ha and 

 320/ha, respectively, but increased in 

 the subtidal channel adjacent to the 

 shell habitat (Fig. 10). The subtidal 

 epibenthos at the shell site in South 

 Channel is composed predominately 

 of wood, bark, and leaves, whereas 

 the subtidal benthic cover at the eel- 

 grass site is primarily shell, eelgrass, 

 and algae; these differences probably 

 contribute to the density differences 

 in mid-June between the two locations. 



n=38 

 P=2.5 



100 

 80" 

 # 60 

 40" 

 20 



n=126 

 P=2.3 



 Cancer magister 



□ Neolrypaea 

 D Upogebia 

 § Crangon 

 H Eogammarus 



□ Nereis 



□ Fish 



'/ rjj Clam siphons 



□ Others 



APRIL MAY EARLY MID JULY AUGUST 

 JUNE JUNE 



Month 



Figure 5 



Diet composition of staghorn sculpin, Leptocottus armatus, from Grays Har- 

 bor, Washington by month, expressed as % IRI. n = number offish examined 

 and P = mean number prey per predator. 



Relative density at shell habitats Sculpin densities 

 at the shell habitat were always higher in the 

 intertidal areas than in the subtidal channel except 

 in mid-June (Fig. 10). In contrast, at the eelgrass 

 site there were higher densities of sculpin in subtidal 

 than in intertidal areas in early June (230 vs. 40 

 sculpin/ha), but by August higher mean sculpin 

 densities occurred in the intertidal areas (138 vs. 30 

 sculpin/ha). 



Discussion 



Importance of crustaceans as prey 



Juvenile staghorn sculpins have been reported to feed 

 heavily on small crustaceans including amphipods 

 and isopods. Studies in Tomales Bay, California 

 (Jones, 1962), and the San Juan Islands, Washing- 

 ton (Thornburgh, 1980), have shown that juvenile 

 sculpin primarily consume amphipods, especially 

 Corophium spp., mysids, and shrimp. Smith (1980) 

 reported that juvenile staghorn sculpin (20-80 mm 

 TL) in Skagit Bay, Washington, consume the amphi- 

 pods Corophium salmonis and Anisogammarus 

 confervicolus, tanaids, and the polychaete Neanthes 

 limnicola. Dinnel et al. (1990) showed ontogenetic 

 diet shifts for staghorn sculpin from Padilla Bay, 



Washington. The smallest sculpin (45-79 mm TL) 

 consumed amphipods and isopods; sculpin 80-119 

 mm consumed amphipods, isopods, and crabs; and 

 the largest sculpin (>120 mm) consumed isopods, 

 crabs, and fish. While juvenile sculpin less than 60 

 mm TL were not sampled in the present study, no 

 significant diet shift was noted for the two size groups 

 (60-119 mm and >120 mm) of the Grays Harbor prey 

 assemblage, although relative importance of items 

 differed between the size groups. Smaller fish did 

 consume a relatively higher proportion of poly- 

 chaetes, whereas larger sculpins consumed more 

 thalassinid shrimp (Fig. 7). 



Other studies have shown that adult staghorn 

 sculpins consume crustaceans as a major portion of 

 their diet when they are available. Dinnel et al. ( 1990 ) 

 found that amphipods, isopods, and an assemblage 

 of crab species (including C. magister and Pinnixa 

 spp.) composed a majority (79% IRI) of the August 

 diets of staghorn sculpins from Padilla Bay, Wash- 

 ington. Data presented by Jones (1962) and Boothe 

 (in Tasto, 1975) showed that the majority of stag- 

 horn sculpin diet (92% IRI) consisted of decapod crus- 

 taceans, including Crangon spp., Upogebia puget- 

 tensis, and a crab assemblage of Cancer sp., Hetni- 

 grapsus sp., Pinnixa sp., and Scleroplax sp. Year- 

 round sampling in Anaheim Bay, California, revealed 

 that sculpin consumed primarily decapod crusta- 

 ceans (78% of the diet by weight) including N. cali- 



