FISHERY BULLETIN: VOL. 73. NO. 4 



Table 3.-Zooplankters and other organisms from stomachs of 140 pink salmon fry (length, 28 to 56 mm) collected in daylight and 30 

 (length, 31 to 58 mm) collected at night in Traitors Cove, 1964-66, and percentage relative importance by volume. 



'+ indicates less than 0.5% 



larvae (up to 8 mm long). Unidentifiable material 

 occurred in only 11% of the stomachs and consti- 

 tuted an insignificant fraction of the volume. 



The 30 pink salmon fry collected from the es- 

 tuary at night all had food in their stomachs, but 

 they probably had not feed recently. Many more 

 food items were found in the stomachs of pink 

 salmon fry collected in daytime than in those 

 collected at night-an average of 136 items versus 

 16. Also, digestion had not progressed as far in the 

 daytime fry-only 11% of their stomachs contained 

 unidentifiable items, whereas 80% of the stomachs 

 from nighttime fry contained unidentifiable 

 items. On three moonlight nights, fry were seen 

 dimpling the water surface while apparently 

 feeding. Incident light intensity at the water sur- 

 face at such times was 0.016 to 1.0 footcandle. 



Stomach Contents of Chum Salmon Fry 



In the springs of 1964, 1965, and 1966, a total of 

 124 chum salmon (length, 32 to .51 mm) were 

 collected from the estuary during daylight and 20 

 (length, 35 to 43 mm) were collected at night 

 (Table 4). All of the fry taken during daylight con- 

 tained food. Copepods occurred in 73% of the 

 stomachs and constituted 30% of the total food 

 volume. Larvaceans occurred in 54% of the 



stomachs and constituted 34% of the total food 

 volume. Dipteran (chironomid) pupae occurred in 

 51% of the stomachs and constituted 11% of the 

 volume. The remaining 25% of the food volume 

 was primarily other planktonic forms (including 

 cladocerans and eggs) but also a few epibenthic 

 animals. Unidentifiable material occurred in 20% 

 of the chum salmon stomachs but constituted an 

 insignificant fraction of the volume and was not 

 included in the final comparisons. Food items eat- 

 en by chum salmon fry were similar in size to 

 those eaten by pink salmon, mostly from 0.3 to 3.0 

 mm long. The largest item was a larval fish 20 mm 

 long. Chum salmon fry, however, tended to feed on 

 larger (Table 5) and harder shelled items than pink 

 salmon, as evidenced by the greater incidence of 

 harpacticoid copepods, collembolans (intertidal 

 springtails), cumaceans, and chironomids in the 

 chum salmon (Tables 3, 4). The chum salmon fry 

 could have picked up some of the so-called 

 epibenthic or intertidal organisms in the form of 

 neuston, or drift material. 



Many more food items were found in the 

 stomachs of the chum salmon collected in daytime 

 than in those collected at night-an average of 124 

 items versus 4. Only 20%of the stomachs collected 

 in daytime contained unidentifiable items versus 

 70% at night. 



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