STOMACH CONTENT ANALYSIS OF TROLL- 



CAUGHT KING AND COHO SALMON, 



SOUTHEASTERN ALASKA, 1957-58 



By 



Gerald M. Reid 

 Fishery Research Biologist 

 Bureau of Commercial Fisheries 

 U.S. Fish and Wildlife Service 

 Juneau, Alaska 



ABSTRACT 



Stomach samples of king salmon (Oncorhynchus tshawytscha) 

 and coho salnnon (Oncorhynchus kisutch) were collected f ronri the 

 comnnercial troll fishery of Southeastern Alaska in 1957 and 1958. 



Herring accounted for the largest percentage of the five organ- 

 isms eaten most frequently by both species of salmon. 



The diet of coho salmon was found to be much more varied than 

 that of king salmon. Differences in the salmons' diet between four geo- 

 graphic areas of Southeastern Alaska and differences occurring in 

 relation to the size of the salmon were analyzed and described. 



INTRODUCTION 



Over the past 30 years the number 

 of troll-fishing vessels in Southeastern 

 Alaska has nearly doubled, but the 

 landings of these vessels, primarily 

 king (Oncorhynchus tshawytscha) and 

 coho('Oo kisutch) saL^lmon, fishermen 

 asserted, have continuously declined. 

 The suggestion has been made that a 

 possible reason for the decline is the 

 depletion of the salmon's food supply 

 brought about by the commercial purse- 

 seine fishery for herring in a number 

 of the troll-fishing areas. 



Similar suggestions were nnade in 

 the State of Washington for the pilchard 

 fishery (Chapman, 1936) and in Brit- 

 ish Columbia for the herring fishery 

 (Pritchard and Tester, 1944). Analyses 

 of the stomachs of king and coho salmon 



in those areas dennonstrated that these 

 salmon have a generally varied diet, 

 and that the relative importance of 

 food items fluctuates between years 

 and by geographical location. 



In 1957 the Bureau of Commercial 

 Fisheries began a study of stomach 

 contents of troll-caught king and coho 

 salmon in Southeastern Alaska. The 

 program was carried on during the 

 commercial fishing season and was 

 primarily aimed at determining the 

 relative importance of herring and 

 other food items in the diet of the two 

 species studied. 



The study was designed to gain 

 basic information on the diet of troll- 

 caught salmon in Southeastern Alaska 

 by examining the occurrence of food 



