TABLE 8. --Trap catches (by month), upstream migrant fish, Brooks River, 



June to September 1957 



loose from the shallow bottom adjacent to the 

 lake outlet on calm days. 



7. All fry migrated out of Brooks Lake 

 tributaries by the first of June. 



H. The shallow shoreline areas of Brooks 

 Lake were almost devoid of rooted aquatic 

 vegetation ffir cover or food until July. 



9. Downstream migrating salmonids were 

 very reluctant to pass between weir pickets 

 during daylight. 



10, Rainbow trout fry were much more 

 evident than sockeye salmon fry in streams 



and in the shallow shoreline areas except 

 during May and June. 



11. During their nesting periods, Arctic 

 terns (Sicrna ])ara(lis<ica) aud greater yellowlegs 

 (Totanus melanolcucus) fed actively on concen- 

 trations of sockeye fry at the mouth of Brooks 

 River. Their predation was minor, considering 

 the tremendous numbers of fry and small 

 numbers of birds. 



12. Migrations of sockeye salmon from 

 Brooks Lake occurred in May and June, and 

 again in late July and mid-Scptcmber. 



PART III. JUVENILE SOCKEYE SALMON LAKE RESIDENCE 



Sockeye salmon are unique among the Pa- 

 cific salmon in their habits during the first 

 year or two of life. Immediately after emerging 

 from the natal gravels, most stocks migrate 

 to a lake where they live for 1 or 2 years. 

 This is an important and critical period in 

 their life because during this time, when they 

 are growing to migratory size, they are vul- 

 nerable to predators coexisting in the lake 

 with them and tf) competition for food between 

 themselves and other fishes. Until 1957 no 

 investigation of lake-dwelling juveniles had 

 been undertaken at Brooks Lake. 



The objectives of the studies were to 

 (1) evaluate the relative merits of tow nets, 

 beach seines, and fine-mesh gill nets as 

 tools for sampling fish; (2) determine seasonal 

 and diurnal changes in vertical and horizontal 

 distribution; (3) determine length and weight 

 by age class; (4) determine food and Its avail- 

 ability through the summer growing season; 

 (5) evaluate the kinds and incidence of para- 

 sites; and (6) evaluate SC;UBA (self-contained 

 underwater breathing apparatus) as a means 

 of observing natural behavior. 



26 



