The incidental catch of 138 adult sockeye 

 salmon did not significantly detract from the 

 production of the 1957 brood year because 

 most of them were released alive. 



Mesh sizes larger than 1 inch were relatively 

 unproductive except for adult sockeye salmon. 

 The 3/4-inch size was by far the most efficient 

 for juvenile sockeye salmon, catching 91 per- 

 cent of the total catch. Sockeye salmon fry 

 were not successfully sampled because the 

 twine on the 1/2-inch size was too thick in 

 proportion to the interstices. 



SEASONAL AND DIURNAL 

 CHANGES IN VERTICAL AND 

 HORIZONTAL DISTRIBUTION 



To make valid comparisons of catches it was 

 necessary to equate nets of different sizes to 

 a standard unit. A standard unit was defined 

 as 75 square feet of mesh; thus each 15- foot- 

 square panel of type I, II, IV, V, and VII nets 

 was equal to three units, and each 50-foot 

 length of Type III and VI nets was equal to 

 four units (fig. 20). 



Even though most catches were made at 

 night, a 24-hour period was used as the stand- 

 ard time unit. Nets were checked once each 

 24-hour period. Thus, a unit of effort was the 

 catch per 75 square feet of a given mesh size 

 in a 24-hour period. Catches of species other 

 than sockeye salmon did not warrant detailed 

 catch per- unit of effort analysis, nor did 

 catches of juvenile sockeye salmon, except 

 for those taken in nets of 3/4-inch mesh. 



A comparison of the monthly catch of 

 sockeye salmon from nets in the littoral area 

 with the catch from nets in midlake shows 

 that littoral sets produced a relatively con- 

 stant catch of about 0.6 sockeye salmon per 

 75 square feet per day, whereas the midlake 

 net's catch increased steadily from to 0.65 

 sockeye salmon per unit per day (table 10). 

 This indicates that sockeye salmon inhabit 

 the shallow shoreline areas in the summer 

 and increasingly disperse into deep water as 

 the season advances. Food studies, as shown 

 later, further substantiated this conclusion. 

 Krogius and Krokhin (1956a) found the same 

 general pattern of progressive migration from 



littoral to pelagic regions in Lake Dalnee, 

 Kamchatka, suggesting that this is a universal 

 behavior trait of juvenile sockeye salmon. If 

 littoral and midlake nets were sampling the 

 same population in proportion to its density, 

 one would expect the catch per hour on littoral 

 sets to diminish as the catch in midlake nets 

 increased. This did not occur, and no explana- 

 tion is offered. 



Table 11 shows the depth distribution of 

 sockeye salmon caught between the surface 

 and the 45-foot depth at midlake stations for 

 28 days on which catches were made. From 

 July 21 through August 22, a type V net was 

 used, simultaneously sampling all depths from 

 to 45 feet. Fifteen, or 79 percent, of the 

 sockeye salmon were caught in the surface 

 net (0-15 feet), while only 4, or 22 percent, 

 were caught from depths of 15 to 45 feet. 

 This is in complete agreement with results 

 from Lake Dalnee, Kamchatka, during the sum- 

 mer months (Krogius and Krokhin, 1948). 



From August 29 through October 6 a type I 

 net was used, permitting sampling only of the 

 0- to 15-foot level (table 11). When catches 

 of the surface net of the entire period are 

 combined, the catch distribution by 5-foot in- 

 tervals in the upper 15 feet substantiates the 

 conclusion that juvenile sockeye salmon were 

 concentrated near the surface to 10 feet, 

 where 91 percent were caught, while only 

 9 percent were caught between 10 and 15 feet. 



To determine the optimum time of day to 

 catch fingerlings with the tow net, three gill 

 nets were checked every 2 hours on August 

 15 and 16. These consisted of two type II nets 

 and one type III net, and all were fished in 

 water less than 15 feet deep. The entire catch 

 was made between midnight and 4 a.m. The 

 night was moonlit and calm, making locating 

 and checking the nets easy. This night's catch 

 indicated that best success with tow nets at 

 the surface in shallow water could be expected 

 around 2 a.m. 



LENGTH AND WEIGHT BY 

 AGE CLASS 



It has been previously shown that age 

 groups of juveniles in Brooks Lake in 1957 



32 



