398 
Fishery Bulletin 108(4) 
Early 
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Late 
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Autumn 
A Deep station (190 m) 
B Shallow station (60 m) 
~Y\ Calanus pacificus 
Other Copepoda 
[] Insecta and Araneae 
Y /\ Cephalopoda 
Ic'/cl Ctenophora 
Decapoda 
Euphausiacea 
| Gammaridea 
[§§§§] Hyperiidea 
Larvacea 
Pteropoda 
Teleostei 
Other 
Size class (mm) 
Figure 3 
Stomach contents of juvenile Chinook salmon (Oncorhynchus tshawytscha) caught at the deep station (A) and shallow sta- 
tion (B) of Dabob Bay, Washington, during different seasons. Collections were made with a midwater trawl and a surface 
tow net at each station on each date. Data were pooled over three years (1985-87) for each season and calculated as the 
normalized biomass of each taxonomic group. 
mostly euphausiids, and the remainder consumed mainly 
gammarid and hyperiid amphipods. In autumn, the 
diet of fish >150 mm from the deep station was com- 
posed more evenly of several prey categories, including 
euphausiids, copepods other than C. pacificus, gammarid 
and hyperiid amphipods, larvaceans, and cephalopods. 
In contrast, prey of chum salmon <150 mm at the 
shallow station were more varied, and few euphausiids 
were present (Fig. 2B). Teleosts and larvaceans, how- 
ever, were represented in similar proportions to those 
at the deep station. Larger chum salmon (>100 mm) 
sampled in early summer were the only group that 
consumed relatively large amounts of ctenophores; the 
remainder of their prey consisted mainly of decapod 
larvae and hyperiids. During late summer at the shal- 
low station, chum salmon consumed decapod larvae, 
gammarid amphipods, copepods other than C. pacificus , 
and larvaceans. Large fish (>150 mm) collected in au- 
tumn fed almost entirely on euphausiids. 
Juvenile Chinook salmon 
There was substantial variation in Chinook salmon 
diets across size classes, seasons, and stations. At the 
deep station during early summer, euphausiids consti- 
tuted a large proportion of the diet of Chinook salmon 
between 75 and 99 mm (Fig 3A). Fish 100-149 mm 
consumed a more evenly distributed mix of prey, domi- 
nated by teleosts and euphausiids. In late summer, 
fish 100-149 mm at the deep station consumed mostly 
hyperiid amphipods and euphausiids. In autumn, fish 
>100 mm at the deep station consumed mostly gam- 
marids, euphausiids, insects, arachnids, cephalopods, 
and hyperiids. 
