BRODEUR and PEARCY: FOOD HABITS AND DIETARY OVERLAP OF SOME SEBASTES 



TABLE 15. — Results of chi-square analyses testing for differences in the occurrence of food and specific prey categories within the 

 various factors. All significances are with three degrees of freedom except where noted. 



Factor 

 analyzed 



Occurrence 

 of food 



Euphausia 

 pacifica 



Thysanoessa 

 spinifera 



Total 

 euphausiids 



Decapods Amphipods Cephalopods Fishes 



• = P - 0.05. " = P • 0.01. •" = P  001 

 1 Significance with two degrees of freedom. 



Gelatinous 

 zooplankton 



25 



20 ■• 



< 



o 



(J 



rr 



UJ 



a. 



o 



t- 

 u. 

 O 



o 



15-' 



S pinniger 



n 



25 



20  



15 •• 



10 • 



5 •• 



S flavidus 



r^ 



o \ >   i ^  ■' '  l m    |   i i i i i i i i  i 1 1 1 | i i i i 



5 10 15 20 25 30 35 



PREY LENGTH INTERVAL (mm) 



FIGURE 9. — Prey size spectra in percent for Sebastes pinniger 

 and S. flavidus. 



ostictus ), they were represented by postlarval 

 or juvenile forms commonly found in the plank- 

 ton. Several comparatively large nektonic fishes 

 and cephalopods (e.g., Clupea harengus pallasi, 

 Sebastes jordani, Loligo opalescens) were eaten, 

 but their occurrences were relatively rare. Con- 

 versely, the virtual absence of many common 

 benthic and epibenthic organisms of appropriate 

 size such as mysids, cumaceans, and gammaridean 

 amphipods further implies that these fish do not 

 normally feed on benthic animals. 



These findings concur with the limited number 

 of previous studies dealing with food habits of off- 

 shore rockfish. Phillips (1964) reported on the diet 

 of all the species included here except S. alutus. 

 Although little taxonomic detail and no quanti- 

 tative data on prey consumption were given, 

 euphausiids were listed as important forage items 

 for all four species. Fishes were also important 

 prey for several species, especially S. flavidus. 

 Skalkin (1964), in a study of S. alutus in the 

 Bering Sea, found mostly euphausiids and cope- 

 pods in the stomachs, but also stated that a few 

 nektobenthic species and "fragments" of benthic 

 echinoderms were present. 



The food habits of S. flavidus have been de- 

 scribed in several studies off Oregon and Wash- 

 ington. Pereyra et al. (1969) found unusually high 

 abundances and volumes of the mesopelagic fish, 

 Stenobrachius leucopsarus, in S. flavidus stom- 

 achs collected near Astoria Canyon and hypothe- 

 sized that local hydrographic conditions may have 

 aggregated these prey at high densities. Gunder- 

 son et al. (1980) 5 reported that S. flavidus off the 

 coast of Washington fed mostly on fishes, includ- 

 ing some pleuronectid fishes possibly eaten near 

 the bottom along with benthic polychaetes. Lorz et 

 al. (1983) found euphausiids dominating the diet 

 of S. flavidus off Washington and Queen Char- 

 lotte Sound, with fishes of greater importance in 

 the latter region. Another deepwater species, 

 S. marinus, found in the North Atlantic Ocean, 

 also fed chiefly on pelagic prey (Lambert 1960). 

 Euphausiids, hyperiid amphipods, and copepods 

 were the most abundant prey, but mesopelagic 

 fishes were also found in large numbers. 



Among the species considered here, two diver- 

 gent feeding patterns are apparent, assuming that 



5 Gunderson, D. R., G. L. Thomas, P. Cullenberg, D. M. Eggers, 

 and R. Thome. 1980. Rockfish investigations off the Wash- 

 ington coast. Ann. Rep., prep, for NMFS, Univ. Wash., 68 p. 



287 



