For each sampling area, the weight of each 

 major food category was calculated as the per- 

 centage of the total dry weight of all food found. 

 The percentage of occurrences and weights of 

 foods were based only on those specimens con- 

 taining food. 



Results 



The foods consumed by seaward-migrating 

 sockeye salmon in Bristol Bay varied in the rela- 

 tive proportion and occurrence of kinds and 

 quantities between months during the summer. 

 The apparent differences between the upper and 

 lower areas of the bay are largely due to date of 

 sampling. The 16 empty stomachs found were col- 

 lected in June from the upper bay — the Kvichak 

 and Egegik areas. 



In early June 1966 in the Kvichak area, 11 of 19 

 juvenile sockeye salmon contained food. Al- 

 though fish and insects made up 97% of the bulk 

 (weight), fish occurred in only 5% of the stomachs 

 and insects in 53%. By late June in the same 

 area, 8 of 10 stomachs contained food, most of 

 which was copepods. They made up 89% of the 

 bulk and were found in 70% of the stomachs; mis- 

 cellaneous crustaceans were found in 60%. In 

 mid- June of the following year (1967), 18 of 21 

 juvenile sockeye salmon from the Kvichak area 

 contained food. Fish, insects, and copepods made 

 up 93% of the bulk; fish occurred in 19% of the 

 stomachs, insects in 76%, and copepods in 62%. 



In mid-June 1966, 20 of 23 stomachs collected 

 farther seaward at Egegik contained very small 

 amounts of food. Euphausiids and miscellaneous 

 crustaceans made up 78% of the bulk, but 

 euphausiids occurred in only 9% of the stomachs 

 and miscellaneous crustaceans in 13%. Insects oc- 

 curred in 48% of the stomachs, but made up only 

 4% of the bulk. 



In mid-July 1966 at Ugashik, all 20 stomachs 

 collected contained larval crustaceans (79% by 



bulk and mostly anomurans). Copepods were in- 

 significant in terms of bulk but occurred in 70% of 

 the stomachs. At Port Heiden (farther seaward) 

 on the same date, fish made up 76% of the bulk of 

 the contents of the seven stomachs collected. Fish 

 occurred in 28% of the stomachs, whereas am- 

 phipods occurred in 71% and insects in 57%. 



At Port Moller in lower Bristol Bay throughout 

 July and on 1 August 1967, copepods made up 

 71% of the bulk of food in 48 stomachs and oc- 

 curred in 85%; larval crustaceans occurred in 

 58%, amphipods in 50%-, and fish in 42%. 



By mid-August 1967, when most juvenile sock- 

 eye salmon have migrated out of Bristol Bay 

 (Straty 1974), the two juveniles taken at Ugashik 

 contained only copepods and insects and two 

 taken at Port Heiden contained mostly fish. 



Only eight juvenile sockeye salmon were taken 

 in September 1966 in the Ugashik area. Copepods 

 and fish accounted for 86% of the stomach con- 

 tents, but only copepods occurred frequently 

 (100%' with copepods vs. 25% with fish). 



As the young sockeye salmon migrated sea- 

 ward over successive months, they ate increasing 

 amounts of food. In the Kvichak and Egegik areas 

 during June, 16 of the 73 stomachs examined 

 were empty and the others had only relatively 

 small amounts of food (average of 3-6 mg). Later 

 in the summer and farther at sea (Ugashik and 

 Port Heiden) the average amount of food per 

 stomach was much greater (20-24 mg), and still 

 later in the summer and farther at sea (Port Mol- 

 ler), the amounts were the highest of all (average 

 of 82 mg). 



In terms of both bulk and frequency of occur- 

 rence, copepods were the most important food of 

 juvenile sockeye salmon in inshore Bristol Bay in 

 1966 and 1967 (Tables 1, 2). Two genera of 

 calanoid copepods {Eurytemora and Metridia) 

 made up 98% of the number of copepods in the 

 stomachs of 50 juveniles taken by Straty and 

 Jaenicke (see footnote 1) in 1967 at Kvichak and 



Table l. — Percentage total dry weight of foods consumed by juvenile sockeye salmon 

 collected at five areas in Bristol Bay, Alaska, 1966 and 1967. 



460 



