Table 13. — Length-frequency distribution of 6,697 juvenile fall chinook salmon from the Snake River collected below 



Brownlee Dam, August 1, 1963 to August 31, 1965 



Number of fish by year and month 



Fork length 



1963 



1964 



Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July 



Mm. 

 240.. 

 235.. 

 230.. 

 225.. 

 220.. 

 215.. 

 210.. 

 205.. 

 200.. 

 195.. 

 190.. 

 186- . 

 180.. 

 176.. 

 170.. 

 166.. 

 160.. 

 165.. 

 160.. 

 146.. 

 140.. 

 136.. 

 130.. 

 125.. 

 120.. 

 115.. 

 110.. 

 106.. 

 100.. 

 95... 

 90... 

 86... 

 80... 

 75... 

 70... 

 65... 

 60... 

 55... 

 50... 

 46... 



1 



3 



8 

 13 

 36 

 42 

 16 . 



4 . 



1 . 



1 . 



2 

 12 

 21 

 13 

 13 



2 



3 



2 . 



1 



1 



7 



13 



14 



22 



7 



2 



1 



1 



7 

 13 

 41 

 48 

 43 

 23 

 12 



6 



2 . 



3 



1 



2 



8 

 25 

 47 

 55 

 26 

 21 



4 



1 . 



3 

 2 

 14 

 7 

 4 

 2 

 6 

 1 



12 



8 

 10 



2 



4 



2 . 



2 . 



1 

 4 

 7 

 10 

 13 

 15 

 32 

 29 

 IS 



1 



4 



11 



7 



12 



28 



60 



45 



61 



55 



56 



68 



74 



104 



102 



98 



31 



19 



1 



1 



Total. 



124 



20 



70 



108 



219 262 361 934 



773 



668 



51 



The average lengths of kokanee differed little 

 in the early and late runs in 1964 (about 5 mm.), 

 but in 1965 the average increased from 105 to 

 138 mm. during a 90-day period in June, July, 

 and August (fig. 10). 



Hatchery-reared sockeye salmon migrated 

 through the reservoir during such a short period 

 in 1965 that size of the fish changed little. The 

 lengths of these fish were 75 to 170 mm. (fig. 11). 



Length-frequency distributions for juvenile 

 rainbow-steelhead trout are given in table 14. 

 Lengths of trout below the dam were 65 to 368 

 mm. The larger fish probably were native rainbow 

 trout rather than the offspring of anadromous 

 steelhead trout. 



EFFECT OF ENVIRONMENT ON 

 EMIGRATION 



The environment significantly affected the pas- 

 sage of juvenile salmon and trout through Brown- 

 lee Reservoir. In 1963, emigration from the 

 reservoir was low when (1) reservoir drawdown 

 in the spring was small, (2) the reservoir was filled 

 early, and (3) maximum discharge was late. 



30 n 

 20- 



10- 







30i 



z 20 



u 



o 



a 



ui 10 . 



a. 







1964 



JUNE 



N=65 

 X= 144 



L 



4ll 



N= 185 

 ji=l28 



L. 



AUGUST 



Ji 



H= 661 

 H: 138 



k 



100 125 150 175 

 FORK LENGTH (MM.) 



r30 



20 •- 



z 



uj 

 u 



-10 «: 



1-30 



20 



100 125 150 175 

 FORK LENGTH (MM.) 



Figure 10. — Length-frequency distribution of 1,043 

 juvenile native kokanee from the Snake River collected 

 below Brownlee Dam, 1964 and 1965. (N= number of 

 fish; 5C indicates average length.) 



256 



U.S. FISH AND WILDLIFE SEEVICE 



