100 



I 



I 

 'lOO 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 21.— CPUE (catch per unit of effort) of sand roller 

 from the main stem of the Yaldma River In 1957 and 

 1958, by sampling site. 



400 



200 



200 



400 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 22.~CPUE (catch per unit of effort) of blueglU 

 and pumpklnseed (combined) from the main stem of the 

 Yakima River In 1957 and 1958, by sampling site. 



200 



1200 



r 



SMALLMOUTH BASS 



LARGEMOUTH BASS 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 23.— CPUE (catch per unit of effort) of smallmouth 

 and largemouth bass from the main stem of the Yakima 

 River In 1957 and 1958, by sampling site. 



400 



200 



= 



200- 



400 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 24.— CPUE (catch per unit of effort) of black crap- 

 ple from the main stem of the Yakima River in 1957 

 and 1958, by sampling site. 



ujlOO 

 2 

 "lOO 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 25.— CPUE (catch per unit of effort) of yellow 

 perch from the main stem of the Yakima River in 1957 

 and 1958, by sampUng site. 



100 - 

 

 100 

 200 



200 - 

 200 



PRICKLY SCULPIN 



MOTTLED SCULPIN 



a. 

 o 



200 

 400 



200 



PIUTE SCULPIN 



TORRENT SCULPIN 



0- 



200 



400, 



50 100 150 200 250 281 



DISTANCE FROM MOUTH OF RIVER (KM.) 



Figure 26.— CPUE (catch per unit of effort) of prickly, 

 mottled, Piute, and torrent sculpln from the main stem 

 of the Yakima River in 1957 and 1958. by sampling site. 



EFFECT OF WATER TEMPERATURE AND 

 FLOW ON DISTRIBUTION OF FISH 



Many environmental factors control the dis- 

 tribution and abundance of fish in the Yakima 

 River. Differences in temperature and velocity 

 of the water, however, so clearly coincided 

 with observed changes in abundance and dis- 

 tribution of some species that we believe they 

 are dominant influences. 



The volume of the Yakima River is low and 

 the surface area relatively high in summer in 

 sections below irrigation and power diver- 

 sions; the low volume of water is heated by 

 air and solar radiation, especially below the 

 Sunnyside and Wapato irrigation diversions 

 (between the sampling sites at km. 145 and 

 153). For example, during the sampling trip 

 of July 15 to August 7, 1957, the average tem- 

 perature for the three sites above these dams 

 was 15° C, and for the three sites below, 

 20° C. The section near the dams also seemed 



15 



