FISHERY BULLETIN: VOL. 82, NO. 2 



mer but to a lesser degree. Thysanoessa spinifera 

 appeared in the stomachs at this time, but E. 

 pacifica continued to be the most important 

 euphausiid consumed. Shrimp and fishes were 

 slightly more important but together made up 

 only a minor portion of the diet. A low percentage 

 of empty stomachs occurred in the summer. 



The diet of S. pinniger in the fall showed 

 substantial shifts in prey composition. Although 

 the frequencies of occurrence were about equal for 

 the two species of euphausiids, T. spinifera great- 

 ly exceeded E. pacifica by weight. Decapods were 

 common but were represented mainly by small 

 shrimp (Sergestes similis) and juvenile pelagic 

 crabs (Munida quadrispina), which contributed 

 little on a weight basis. Amphipods and gelatinous 

 zooplankton occurred frequently but were not 

 important by weight. Fishes were important by 

 occurrence and weight and consisted mostly of 

 mesopelagic species and several adult Sebastes 

 jordani which made a large contribution to the 

 biomass consumed. 



Almost one-quarter of the fish collected in the 

 winter had empty stomachs and contained much 

 digested material. Euphausia pacifica and 71 

 spinifera occurred in about the same number of 

 stomachs, but E. pacifica contributed over twice 

 as much of the total weight as T. spinifera. 

 Subadult E. pacifica were very numerous at 

 this time. The fishes consumed were mostly meso- 

 pelagic species. 



Sebastes flavidus showed similar trends in 

 food resource utilization among the three seasons 

 from which collections were made (Table 11). 

 Euphausiids, consisting mostly of E. pacifica, 



made up two-thirds of the diet by weight in the 

 summer. Fishes were common and contributed 

 heavily to the total biomass. Cephalopods were 

 next in importance by either occurrence or weight. 

 The diet in the fall showed the same shift in 

 euphausiid species as was apparent for 8. pinni- 

 ger, with T. spinifera the dominant species. Fishes 

 were almost as important by weight as euphau- 

 siids, but their weight total was mostly composed 

 of adult clupeids. Cephalopods were least impor- 

 tant in the fall months. 



Euphausiids represented about half the diet 

 during the winter, but the remainder was shared 

 mostly by cephalopods and fishes. Both species of 

 euphausiids were commonly found, but E. pacifica 

 (mostly subadults) were slightly more important 

 in the overall diet. Cephalopods (mostly adult 

 Loligo opalescens and juvenile copepods) did show 

 a substantial increase in weight and occurrence 

 during these months. Fishes were found in over 

 half the stomachs but were mainly juveniles 

 of relatively small myctophids. Gelatinous zoo- 

 plankton were most common, and decapods were 

 least common, during this season. In contrast to 

 S. pinniger, all stomachs of this species contained 

 some food and many stomachs were full during 

 this season. 



Geographic Variation 



Several trends were evident when comparing 

 the diet of S. pinniger between regions (Table 12). 

 The two southernmost regions had similar diets 

 dominated by E. pacifica with T. spinifera repre- 

 senting only a minor portion of the diet. Meso- 



TABLE 12. — Variation in major prey taxa composition with geographic area for Sebastes pinniger and S. flavidus. F.O. = frequency 

 of occurrence; % W = percent gravimetric composition; + = a prey category was present but made up < 0.1% of the total weight. 



' No stomachs of S pinniger were collected from this region 



282 



