I 



HOAG: SUMMER FOOD OF JUVENILE SOCKEYE SALMON 

 IOOt 



lOOn 



«> 

 ■S 







41 



25 50 75 



Percentage of Cyclops in fry diet 



100 



25 50 75 



Percentage of Bosmina in fry diet 



100 



Figure 4. — Relationship between the percentage of 

 Cyclops in the foregut of fry and yearlings. 



and Narver (1970) showed diel and depth 

 changes in the food of juvenile sockeye salmon 

 in Babine Lake, British Columbia. 



Food selection depends on characteristics of 

 the feeder and food items (Ivlev, 1961) and prob- 

 ably occurs in some degree for all species. In 

 this study, the cause of the discrepancy between 

 the composition of the foregut and zooplankton 

 samples cannot be attributed specifically either 

 to sampling error or to selective feeding. What- 

 ever the cause, the degree of discrepancy was 

 small, and I concluded that the zooplankton sam- 

 ples generally reflect available food in Iliamna 

 Lake. This is in contrast to Narver ( 1970) , who 

 found that juvenile sockeye salmon strongly 

 selected numerically less abundant zooplankters 

 in Babine Lake. 



ACKNOWLEDGMENTS 



Dr. Ole A. Mathisen gave advice and encour- 

 agement during the study and critically reviewed 

 the manuscript; Drs. Robert L. Burgner, David 

 W. Narver, and Donald E. Rogers critically re- 

 viewed the manuscript; Dr. Tor B. Gunnerod 

 conducted the zooplankton sampling and re- 



FiGURE 5. — Relationship between the percentage of 

 Bosmina in the foregut of fry and yearlings. 



viewed the manuscript; and Orra E. Kerns, Jr. 

 and John W. Anderson assisted in the collection 

 of fish samples. 



LITERATURE CITED 



Bond, C. E., and C. D. Becker. 



1963. Key to the fishes of the Kvichak River sys- 

 tem. Fish. Res. Inst. Coll. Fish. Univ. Wash. 

 Circ. 189, 9 p. 



Fowler, C. W., and W. H. Lenarz. 



1965. Iliamna Lake limnetic zooplankton studies. 

 In J. D. McPhail (editor), Research in fisheries 

 .... 1964, p. 16-18. Coll. Fish. Fish. Res. Inst. 

 Univ. Wash. Contrib. 184. 



Ivlev, V. S. 



1961. Experimental ecology of the feeding of fishes. 

 (Translated from the Russian by Douglas Scott.) 

 Yale Univ. Press, New Haven, 302 p. 

 Lenarz, W. H.^ 



1966. Population dynamics of Cyclops scidifer and 

 an evaluation of a sampling program for estimat- 

 ing the standing crop of zooplankton in Iliamna 

 Lake. M.S. Thesis, Univ. Washington, Seattle, 

 120 p. 



Narver, D. W. 



1970. Diel vertical movements and feeding of 

 underyearling sockeye salmon and the limnetic 

 zooplankton in Babine Lake, British Columbia. 

 J. Fish. Res. Board Can. 27:281-316. 



361 



