458 



Fishery Bulletin 93(3), 1995 



GRAYS HARBOR i , 



WASHINGTON 



Westport 



E eelgrass 



S shell 



, * Subtddal 



Intettidal 



Figure 1 



Grays Harbor, Washington, sampling locations for staghorn sculpin, Leptocottus 

 armatus, and Dungeness crab, Cancer magister, at eelgrass (E) and shell (S) 

 sampling sites. Bold dashed line denotes intertidal trawls and lighter dashed 

 line indicates subtidal channel trawls. 



eelgrass, terrestrial leaves), shell, and underlying 

 substrate. All fish and crab were sorted from the 

 catch, identified to species, and counted. Crab were 

 measured (carapace width [CW] inside the 10th lat- 

 eral spine), sexed, and returned to the water. Stag- 

 horn sculpin were picked from the catch and killed. 

 Their body wall was slit, and the fish were preserved 

 in 10% formalin in sea water and later transferred 

 to 70% ethanol in the lab for measurement (total 

 length, TL) and stomach content analyses. 



Length-frequency data for sculpin and crab were 

 used to determine instar and year-class composition. 

 Crab length-frequency histograms by trip were used 

 to establish the presence of the 1989 year class of 0+ 

 crab from first tentative appearance in May, at peak 

 settlement in early June, and at the time of summer 

 growth through August. Size modes for crab instars 

 (juvenile crab 6-40 mm CW) were visually deter- 

 mined from length-frequency histograms (hereafter 

 crab instars 1 through 7 will be referred to as J1-J7 

 and conform to instar sizes specified by Wainwright 

 and Armstrong [1993] and Dinnel et al. [1993]). 

 Evaluation of size ranges and modes as compared 

 with stage (CW for crab; TL for sculpin, Tasto, 1975) 

 were used to set the upper size limits for 0+ and 1+ 

 age classes each month during the summer. 



Sculpin gape measurements 



Sculpin mouth widths (measured for 466 sculpin) 

 were used as an index of mouth gape size. The mouth 



of a preserved specimen was gently 

 pried open as far as possible and the 

 internal distance from the intersections 

 of upper and lower jaws was measured. 

 Since fish body lengths are more com- 

 monly reported as standard lengths 

 (SL), sculpin total lengths (TL) were 

 converted to standard length for a dis- 

 cussion of mouth gape to body length 

 relationship 8 : 



SL = 0.87338 TL - 2.7584 

 (r 2 = 0.995, n = 53). 



Stomach content analyses 



Stomach contents of all staghorn 

 sculpin from a trawl were examined up 

 to a total of 20 fish. When catches were 

 higher, the fish were separated into 5- 

 mm size intervals, then proportionally 

 subsampled until a total of 20 fish were 

 selected for stomach analyses. Sculpin 

 were measured (TL), blotted on paper 

 towels, and weighed wet to the nearest 0.1 g. Then 

 their stomachs were removed, blotted, and weighed 

 with and without contents to derive stomach content 

 weight. An estimate of relative stomach fullness was 

 derived by using six categories corresponding to 

 empty, 1/4, 1/2, 3/4 full, full, and "distended." In the 

 latter case, quantity of prey within the stomach re- 

 sulted in pronounced distention of the body wall be- 

 yond the normal lines and curvature of the fish. 

 Sculpin stomachs were analyzed to document the 

 frequency of occurrence of Dungeness crab, the over- 

 all proportion of the diet attributed to major prey 

 categories, and the relationship between sculpin size 

 and size of juvenile crab prey. 



Food items were generally identified to species 

 unless obscured by digestion. Prey species consumed 

 frequently were analyzed as a distinct prey category, 

 but species that were consumed infrequently were 

 combined to form a more general prey taxon that also 

 included prey items obscurred by digestion. As an 

 example, the amphipod Eogammarus confervicola 

 was recorded as a separate prey category owing to 

 its high frequency of occurrence, but several species 

 of fishes (Gasterosteus aculeatus, Lumpenus sagitta, 

 Cymatogaster aggregata, Leptocottus armatus, 

 Pleuronectes vetulus, and Citharichthys sp.) were 

 consumed infrequently and were thus grouped as 

 "fish." Analysis of stomach content data was done by 



8 Williams, G. Pacific Estuarine Research Labs., San Diego State 

 Univ., San Diego, CA. Unpubl. data, 1991. 



