Sturdevant et al.: Feeding habits, prey fields, and potential competition of Theragra cho/cogramma and Clupeo pallasi 
491 
along with euphausiids and hyperiids, formed larger di- 
etary components at that time. In autumn (October 1995), 
pollock strongly selected for large calanoid copepods and 
herring strongly selected for larvaceans (Figs. 3-5). Addi- 
tional differences were noted in terms of prey frequency. 
In summer, pollock consumed hyperiids more frequently 
than they consumed euphausiids, and in autumn, both 
pollock and herring consumed euphausiids more frequent- 
ly than hyperiids. 
Seasonal feeding 
Several measures of feeding in autumn indicated that 
YOY pollock continued to feed moderately, whereas the 
pattern for YOY herring showed more of a decline from 
summer (Tables 1 and 3). Very similar high percentages 
of pollock and herring had fed in summer and in October 
1995 (>80%), but in November 1994, the percentage of 
nonfeeding herring was greater than the percentage of 
feeding herring, and was more than twice the percentage 
of nonfeeding pollock (Table 3). For pollock, the November 
1994 feeding measures were only lower than the high 
summer measures, whereas for herring, feeding measures 
in autumn of 1994 were lower than in either summer 
or autumn of 1995. Although pollock stomachs were at 
least half full in each season, herring stomach fullness 
declined from 75% full in summer to half full in October 
1995, to only trace amounts of food in November 1994. 
Similarly, prey content %-BW declined less between sea- 
sons for pollock than for herring. Total prey numbers and 
weights were generally lower for pollock than for herring 
in a season, but numbers of prey were highly variable and 
biomass of prey was relatively stable for pollock, whereas 
these measures showed declining trends for herring (Fig. 6, 
Table 3). 
Digestion data and feeding-frequency data for individ- 
ual fish were pooled across seasons to compare day and 
night feeding patterns. The condition of stomach contents 
