Armstrong et al.: Food habits of Leptocottus armatus 



465 



tion at this time of year. We examined well-pre- 

 served specimens of this polychaete from stom- 

 ach contents but found all were immature. High 

 predation on immature stages of N. brandti may 

 indicate worms are leaving their burrows to dis- 

 perse as described by Dean (1978). By July and 

 August, the behavior of the polychaetes may have 

 changed, or their abundance may have declined 

 since worms were rarely observed from stomach 

 contents during those months. 



Dungeness crab 



Predation on 0+ Dungeness crab by sculpin is 

 of interest because of the substantial commer- 

 cial value of the C. magister fishery from north- 

 ern California through southeast Alaska 

 (Botsford et al., 1989) and because of the eco- 

 logical implications of this estuarine predator- 

 prey relation that is dependent on the annual 

 arrival of oceanic crab larvae. Estuaries are 

 important nursery grounds for 0+ crab (Cleaver, 

 1949; Tasto, 1983; Gunderson et al., 1990) and 

 provide refuge by means of several habitats in- 

 cluding eelgrass and epibenthic shell (Stevens 

 and Armstrong, 1985; Gunderson et al., 1990; 

 Jamieson and Armstrong, 1991; Dumbauld et al., 

 1993). Fernandez et al. (1993a) demonstrated 

 that megalopae and newly settled 0+ C. 

 magister prefer heavy shell habitat over eel- 

 grass, mud with scattered shell, or bare mud. In 

 addition, field tethering of crab in Grays Harbor 

 showed that shell provided the best protection 

 from predation compared with other habitats and 

 that crab tethered with attached hooks were most 

 often attacked by staghorn sculpin. 



During peak crab settlement in early June, 

 juvenile crab were found in 42% of the sculpin 

 stomachs examined and represented 10% of the 

 total diet by weight (%GC), or 24% of IRI (Fig. 

 5). At this time crab are highly vulnerable to 

 predation; the small Jl and J2 instars (6-11 

 mm CW) are very abundant (over 100/m 2 ; Fernandez 

 et al., 1993b), compete for limited refuge habitat, and 

 molt frequently (every 2—3 weeks; Wainwright and 

 Armstrong, 1993). The temporal pattern of 0+ inter- 

 tidal density is consistent with inferences regarding 

 both the rapid predation of much of the 0+ crab popu- 

 lation shortly after settlement and with the relative 

 importance of epibenthic shell as a refuge to ensure 

 some survival of the year class. From early June to 

 July, 0+ density decreased an order of magnitude at 

 both the intertidal shell and eelgrass sites as mea- 

 sured by trawl, but density was generally about three 

 times higher over shell habitat compared with eel- 



grass habitat (Fig. 10). This difference in density 

 between the two habitats is likely much greater than 

 that indicated by the trawl data. Net efficiency is 

 unknown, but the gear was designed to operate on a 

 fairly uniform sand-mud substrate (Gunderson and 

 Ellis, 1986) and, we assume, is less efficient over the 

 shell habitat compared with eelgrass habitat (al- 

 though much shell is taken in trawls). More impor- 

 tantly, the net "integrates" animals and material 

 along the trawl path and cannot provide distinctions 

 over smaller spatial scales of highly heterogeneous 

 habitat such as intertidal shell. We know from pre- 

 vious intertidal work done in Grays Harbor that 



