OCCURRENCE OF Sg'^ 



SUMMARY AND DISCUSSION 



The 1957 return of blueback was of 

 special interest since the U^g'^ ^^^^ ^® 

 progeny of the 1953 escapement which was 

 one of the largest in recent years. The 

 most unusual feature of the 1953 r^"i was 

 that over 86 percent of the Okanogan 

 spawners were 3-y6*r-old fish whose sex 

 ratio of males to females was 1:0. 75- 1^ 

 hulk of these 3-year-old fish escape the 

 fishery and continue to the Okanogan where 

 in normal years they comprise about 22 

 percent of the spawning population. These 

 pm ^n fish seem to be peculiar to the 

 Okanogan £uid su« seldom encountered in the 

 other two systems. Table 6 demonstrates 

 the occurrence of 3-year-old Columbia 

 River blueback for the last 7 years. 



The ccHDparatively low return to the 

 Okanogan this year may be peo-tly attri- 

 buted to the high proportion of 3-year-old 

 fish in the 1953 run. Lower fecundity and 

 possibly lower fertility linked with re- 

 duced survivfiLL of eggs, fry, and finger- 

 lings because of their small size may be 

 factors contributing to the low return. 



DISTRIHJTION 



The 1957 Rock Island count of blue- 

 back salmon was the smallest recorded since 

 1950. This decline was more evident in 

 the Okanogan than in the Wenatcfaee system. 

 It has been speculated that lower fecundity 

 and poor survival of the spawn of the 32'"* 

 that made up 86 percent of the Okanogan 

 run in 1953 was a factor in this year's 

 low return. 



The 1957 spawning escapement to the 

 Okanogan was composed of 30 percent 32 's 

 and 70 percent 42's. The sex ratios of 

 the two age cleisses were widely divergent. 

 The 32 's had 35 percent females and the 

 U2's had 62 percent females. 



Spawning success was good and ap- 

 parently was not affected by the delays 

 caused by the drop structures. However, 

 the drop at many of the structures was 

 considerably greater than anticipated, 

 and some modification may be necessary to 

 increase the ease of fish peissage at these 

 structures. 



In gener€il the escapement was ade- 

 quate and spawning appeared to be success- 

 ful. 



The distribution on the spawning 

 grounds has not changed appreciably in the 

 last 5 years. The one exception is section 

 M-N, which for all practical purposes sup- 

 ported no spawning this year (fig. h). 

 During the past 5 years section M-N sup- 

 ported an average of only 7 percent of the 

 spawners. 



LITERATURE CITED 



GANGMARK, HAROLD A. , AND LEONARD A. FULTON 

 1952. Status of Columbia River blue- 



back runs, 1951. U. S. Fish and 

 Wildlife Service, Special Scien- 

 tific Report— Fisheries No. Jk, 

 29 pp. 



EXPERIMENTAL CHANNEL 



Channel improvement work in sections 

 B to D was responsible for reducing the 

 flow in the experimental channel to a mere 

 fraction of normal. Consequently, only 88 

 fish were observed spawning in this channel 

 compared to 2,600 for last year. This same 

 channel work seriously reduced the flow in 

 the west channel causing an additional loss 

 of spawning area. 



