Table ^.--Spawning ground peak counts of spring and summer chlnook saljnon In tributaries above Rocl^ 



Reach Dam, 1954-60 — Continued 



[nc=no count] 



Race and stream sections 



Year 



1954 



1955 



1956 



1957 



1958 



1959 



1960 



Period of 



peak of 



spawning 



Okanogan River: 



Oroville to Tonasket 



Tonasket to Riverside 



Riverside to Qnak Bridge 



Qmak Bridge to Mallot 



Mallot to Jtonse 



Jfonse to Columbia River 



Total 



Numbers of fish estimated' . . . 

 Summer chinook salmon totals. 



1 



13 

 2 



21 

 

 





 17 



5 

 24 



5 



2 



3 

 43 



7 

 35 



6 







3 

 21 



1 



20 



5 











16 



1 



S 



4 

 



10/15-10/25 

 10/15-10/25 

 10/15-10/25 

 10/15-10/25 

 10/15-10/25 

 10/15-10/25 

 10/15-10/25 



37 



53 



94 



50 



29 



191 



338 



180 



104 



539 



1,807 



1,582 



737 



838 



^ Survey occurred after peak spawning. 

 ^ Partial area count. 



' Counts were probably of a mixture of spring and summer chinook as surveys occurred between spawning peak period 

 of the two races. 



' Survey occurred prior to peak of spawning. 



' Estimated number of fish based on 3.6 fish per redd. 



Stream and the relative importance of the 

 various streams. 



The Chewack River and the upper Methow 

 River are the most important spring chinook 

 salmon streams above Rocky Reach Dam, 

 In the Wenatchee River system most spring 

 chinook spawners are found in Chiwawa River 

 and Nason Creek with peak abundance vary- 

 ing between the two streams in different 

 years. The spring chinook salmon survey 

 counts in the Entiat River in 1960 were 

 the highest of the 6 years of stream surveys. 

 This occurred in a year when generally fewer 

 spawners were counted in all the other streams. 



Summer chinook salmon spawn mainly in 

 the Methow and Wenatchee Rivers; the latter 

 is by far the more important. 



The chronology of peak spawning periods 

 for chinook salmon in the upper Columbia 

 River system appeared to be associated with 

 stream temperatures. Spring chinook salmon 

 spawned earliest, mostly in August, when 

 water temperatures in the spawning areas 

 ranged from 48° to 55° F, Within a stream, 

 spring chinook salmon in the upper sec- 

 tions were found to spawn earlier than spring 

 chinooks in the lower sections. Nason Creek 

 (table 5) is a good example. Here, at the 

 time spring chinook salmon were spawning 

 in the upper sections in water temperatures 

 of around 50°-55° F. , those in the lower 

 sections were congregated in pools where 

 water temperatures were around 60 F. Later, 

 as the water temperature in the lower sec- 



tions dropped to the range of 50°- 55°, these 

 fish moved onto the spawning riffles. Sum- 

 mer chinook salmon spawned later in the 

 season (October) when water temperatures 

 in these spawning areas had fallen to 50°- 

 55° F. 



Length frequency .- -Lengths (mideye to end 

 of hypural plate) of dead spawned fish were 

 taken to determine if age classes could be 

 differentiated by modal groups (tables 6 and 7). 

 Ages could not be read from scales because 

 of scale absorption on the spawned fish. Al- 

 though modal groups are evident, more so 

 among spring than summers, there is too 

 much overlap of lengths to distinguish age 

 classes without corroborating evidence, ex- 

 cept possibly for jack chinook salmon. Jack 

 chinook salmon are precocious males, re- 

 turning from the ocean in the year following 

 their seaward migration, with lengths (mid- 

 eye-hypural plate) ranging from approxi- 

 mately 300 mm. to 450 mm, for spring 

 chinook salmon and from approximately 280 

 mm. to 400 mm. for summer chinook 

 salmon. 



Although these data do not show dif- 

 ferentiation of all age groups, they illus- 

 trate that main size groups, consisting 

 of probably several age groups, are usually 

 present in all tributaries each year. One 

 exception was found in the Chewack 

 River for 1957 where large chinook 

 salmon of both sexes were notice- 

 ably absent, Sumnner chinook salmon 



