ECOLOGICAL STUDIES OF SOCKEYE 



SALMON AND RELATED LIMNOLOGICAL 



AND CLIMATOLOGICAL INVESTIGATIONS, 



BROOKS LAKE, ALASKA, 1957 



by 



Theodore R. Merrell, Jr. 



Fishery Research Biologist 



Bureau of Commercial Fisheries Biological Laboratory 



U.S. Fish and Wildlife Service 



Auke Bay, Alaska 



ABSTRACT 



Ecological studies on the fresh-water phases of the life history of sockeye 

 salmon and studies on related limnology and climatology were made at Brooks Lake, 

 Alaska, in 1957. 



Data are presented and interpreted on adult sockeye salmon spawning distribu- 

 tion and behavior, age, sex, length, fecundity, and bear predation; on juvenile sock- 

 eye salmon ages, food, growth, migration from the lake, relative abundance, and 

 distribution In the lake; and on climatological and limnological factors that may 

 influence sockeye salmon behavior and abundance. 



INTRODUCTION 



Brooks Lake is located on the Alaska 

 Peninsula 45 miles east of Bristol Bay (fig. 1). 

 It is about 1 1 miles long and 2 to 4 miles wide, 

 and flows into Naknek Lake via Brooks River. 

 All five species of North American salmon 

 utilize the lake or its tributaries for spawning, 

 bat the sockeye ealmon, Oncorhynchus nerka 

 (Walbaum), is the most abundant. A significant 

 portion of the commercially valuable Bristol 

 Bay sockeye salmon run ie produced in Brooks 

 Lake and its ouilet stream. Brooks River. 



The purpose of the research program at 

 Brooks Lake is to determine the factors that 

 influence abundance and survival of sockeye 

 salmon during their fresh-water life. Knowl- 

 edge of these factors would assist management 

 of the fishery for maximum production. 



Except for 1943, data on adult sockeye 

 salmon have been obtained since 1940 at a weir 

 at the outlet of the lake where the Bureau of 

 Commercial Fisheries maintains a Biological 

 Field Station (fig. 2). In addition to the studies 

 at the weir, since 1947 investigations have 

 been made of juvenile sockeye salmon and of 

 limnology and climatology. 



This paper reports the results of investiga- 

 tions at the Brooks Lake Field Station in 1957, 

 when an expanded program of basic research 

 on sockeye salmon was begun. The discussion 

 Is in four parts: I, adult sockeye salmon; 

 II, seaward migration of juvenile sockeye 

 salmon; III, lake residence of juvenile sockeye 

 salmon; and IV, limnology and its relation to 

 sockeye salmon. 



