days until maximum density for that wave 

 has been reached would explain the shape of 

 the curve comprising each of the 2-week-long 

 peaks (fig. 9). 



the bears caused a mass evacuation of the 

 stream and return to the relative safety of 

 the lake. 



MASS MOVEMENTS OF SPAWNING 

 SOCKEYE SALMON FROM 

 BROOKS LAKE 



Since mass movements of salmon from 

 Brooks Lake to One Shot Creek and back 

 to the lake had been reported in previous 

 years, we set up a 10-foot tower near the 

 mouth of the creek to observe upstream and 

 downstream migrations. The first small school 

 of salmon was seen July 24. The school 

 gradually increased in size and between Aug- 

 ust 16 and 20 milled about the mouth of One 

 Shot Creek. On August 21 the school entered 

 the stream and migrated upstream to spawn. 



A diurnal movement of salmon in and out 

 of Hidden Creek was observed on August 6. 

 During the afternoon of August 5, a large 

 school was in the lake off the mouth of the 

 creek. On the morning of the 6th the school 

 was still there, and no fish were in the creek. 

 At 1 p.m. several hundred ascended the 

 creek for 500 yards, but at 2 p.m. they all 

 turned suddenly and descended to the lake. 

 Their return to the lake coincided with the 

 appearance of two bears in the stream 400 

 yards above the mouth. By 4 p.m. only a few 

 fish remained in Hidden Creek, and these were 

 near the mouth. Apparently the appearance of 



LAKE BEACH SPAWNING 



Sockeye salmon are known to spawn on suit- 

 able beaches in many areas, and spawning 

 has been reported along the beach of Brooks 

 Lake between the outlet and Up-a-tree Creek 

 (Richard Straty, personal communication). 

 From mid-July until mid-September, we sur- 

 veyed the gravelly beaches in shallow water 

 around the Brooks Lake shoreline from boats. 

 On September 14 during an aerial reconnais- 

 sance of the lake shoreline, we saw several 

 hundred sockeye salmon spawning in shallow 

 water along a mile of beach north of the 

 mouth of Up)-a-tree Creek. The same area 

 was surveyed by boat on 3 days with the 

 following results: 



Date 



September 15 

 September 22 

 October 4 



Number 

 of adults 



357 



278 



59 



Number 

 of redds 



146 



Not counted 



136 



Since the fish and redds were clearly visible 

 in the shallow water, the maximum count 

 may be regarded as a close approximation 

 of the total numbers of beach spawners. 

 Beach spawning was a minor factor in Brooks 

 Lake production in 1957. 



PART II. JUVENILE SOCKEYE SALMON SEAWARD MIGRATION 



In the spring juvenile sockeye salmon' 

 migrate to the sea from their lake nursery 

 area where they have spent the previous 1 or 

 2 years. This migration provides an oppor- 



'I define juvenile salmon as any young salmon. In 

 the life history stage between hatching and migration 

 to the sea. Fry are salmon In their first year of life. 

 Including the period between hatching and the first 

 winter. Yearlings are salmon in their second year of 

 life. Including the period between the first and second 

 winters. Two-year-olds are salmon in their third year 

 of life, between the second and third winters. 



tunity to evaluate survival from the parent 

 run and to study characteristics of the sea- 

 ward migration. 



Five aspects of the seaward migration of 

 juvenile sockeye salmon were investigated at 

 Brooks Lake in 1957: (1) Age and length 

 composition of seaward migrants; (2) seasonal 

 length- weight relationship of juvenile migrants 

 by age groups; (3) characteristics of daily and 

 seasonal migration by age group of sockeye 

 salmon and of other species migrating out of 

 the lake; (4) migration of Juveniles upstream 



17 



