PART I. ADULT SOCKEYE SALMON 



The objectives of the investigations of adult 

 sockeye salmon were to (1) estimate numbers 

 of spawners; (2) determine age and length 

 composition, sex ratio, and fecundity of the 

 spawning population; (3) relate the distribution 

 of adults on the spawning grounds to time of 

 passage and abundance at the weir; (4) deter- 

 mine success of spawning; (5) determine rate 

 of disappearance of carcasses after spawning 

 (6) determine effects of bear predation; (7) ob- 

 serve spawning behavior; (8) evaluate mass 

 movements of sockeye salmon into small tribu- 

 taries from the lake; and (9) evaluate the im- 

 portance of lake beach spawning on sockeye 

 salmon production of the lake. 



NUMBERS OF SPAWNERS 



The counting weir was installed June 18 and 

 was operated until October 5. It had no fixed 

 openings; 10 to 20 pickets were removed at 

 any point where fish congregated below the 

 weir, and fish were counted as they passed 

 through the gap. Multiple-unit hand tallies 

 were used to record both upstream and down- 

 stream migrants. Early in the season counters 



sat on planks suspended from bipods support- 

 ing the weir, but since their presence dis- 

 turbed the fish, the counters changed and stood 

 in the stream several feet from the down- 

 stream side of the opening in the weir. To 

 assure good visibility, observers always wore 

 polarizing sun glasses. 



The first migrants appeared at the weir on 

 June 25 when 30 were counted (fig. 3). Up- 

 stream migration was characterized by 

 one major peak within which were three 

 minor peaks. So that fish from the different 

 peaks could be recognized on the spawning 

 grounds, some from each peak were tagged 

 with Petersen disk tags with distinctive 

 color combinations. One combination was used 

 from June 25 to July 14, a second from July 

 14 to 19, and a third from July 19 to the end 

 of the migration. 



On July 10 a small school of adults was 

 observed for the first time at the upstream 

 side of the weir, and as the season progressed 

 the school grew larger. Occasionally it moved 

 out of the area for several hours or would be 



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25 30 10 20 

 JUNE JULY 



10 20 30 

 AUGUST 



Figure 3.--Daily and cumulative totals of migrating adult sockeye salmon at Brooks Lake 



weir in 1957. 



