the species downstream usually indicate warm 

 water; we, therefore, assumed that the main 

 reason for the difference in composition of 

 species was water temperature. 



Temperatures in smaller stretches of the 

 Yakima River also seem to influence the 

 distribution of some fish. For example, sum- 

 mer temperatures were lower in the canyons 

 from km. 177 to 201 and 233 to 250 than in the 

 valleys. Few cyprinids and catostonnids were 

 observed in canyon areas compared with the 

 sampling sites in the open valleys. 



Throughout the study, few fish were taken 

 from km. 69 to 89. Here the drop in elevation 

 (fig. 2) and the water velocity are low, and the 

 bottom is mud and sand (table 1). The riffles 

 and rock bottoms in adjacent portions of the 

 Yakima River are lacking in this area. Al- 

 though six species of fishes were conr^monly 

 taken in warm water of low velocity (table 6), 

 the only one to frequent km. 60 to 89 con- 

 sistently was the carp. Evidently the other 

 species were not adapted to the environment 

 in this part of the river. 



FISH SPECIES THAT RESIDE WITH 

 JUVENILE SALMON 



The location of spawning grounds and be- 

 havior of the juvenile salmon before and during 

 seaward migration determine the area in the 

 Yakima River where young salmon and asso- 

 ciated fish live. These factors vary within and 

 between the species of salmon. 



Juvenile coho and spring chinook salmon 

 would be strongly influenced by the other fish 

 above km. 153 because they live in this por- 

 tion of the Yakima River during their first 

 year of life. Salmon reside with 2 5 nonsalmon 

 species above km. 153; salmon are generally 

 more abundant than the cyprinids and catostom- 

 ids. Juvenile coho and spring chinook salmon 

 are more closely associated with other salmon, 

 trout, and sculpins. In the spring of their sec- 

 ond year of life, coho and spring chinook salmon 

 migrate to sea and must pass through dense 

 populations of resident fishes in the central and 

 lower portions of the Yakima River (fig. 7). 



Fall chinook salmon spawn below km. 153, 

 and their progeny emerge from the gravel into 

 an area inhabited by 27 nonsalmon species. The 

 abundance of cyprinids, catostomids, and cen- 

 trarchids is high. The duration of this associ- 

 ation is short because of the early migration of 

 fall chinook salmon fry, but the exact effects of 

 these fish on the salmon are unknown. 



SUMMARY 



We studied a large tributary of the Columbia 

 River to obtain information on the abundance 

 and distribution of fish that live with juvenile 

 salmon. This information is needed to under- 

 stand how other species may limit the pro- 

 duction of salmon. 



Fish populations were sampled at 35 sites 

 in the main stem (lower 2 81 km.) of the Yakima 

 River at approximately 2-month intervals for 

 13 months in 1957 and 1958. Thirty-three of 

 the 37 species of fish known from the Yakima 

 were taken in collections numbering 34,733 

 specimens. Distribution and abundance are 

 given for species and family groups. Dominant 

 families by decreasing order of abundance 

 were: Cyprinidae, Catostomidae, Salmonidae, 

 Cottidae, and Centrarchidae. Dominant spe- 

 cies by decreasing order of abundance were: 

 chiselmouth, redside shiner, northern squaw- 

 fish, largescale sucker, speckled dace, moun- 

 tain whitefish, torrent sculpin, salmon (chinook 

 and coho salmon combined), and carp. The dis- 

 tribution of fish in the Yakima River appears 

 to be affected by summer water temperatures. 

 Cold-water type fish are generally above 

 km. 153 and warm-water type fish below this 

 point. The section between km, 72 and 89 of 

 the Yakima River which has low velocity, high 

 summer temperatures, and a mud and silt 

 bottom, has the fewest species and lowest 

 numbers of fish. 



The main spawning area of coho and spring 

 chinook salmon is between km. 2 50 and 281. 

 Their progeny live with 25 other species of 

 fish for a prolonged period during presmolt 

 stages, after which they pass (on their seaward 

 migration) through the Yakima River's popu- 

 lations of 32 nonsalmon species. 



Fall chinook salmon en^erge from redds 

 below km. 153 and are exposed immediately to 

 27 species of fish, and to greater numbers of 

 predatory fishes than the coho and spring 

 chinook salmon. The duration of this exposure 

 is less, however, as fall chinook salmon mi- 

 grate to the sea during the spring soon after 

 their emergence from the gravel. 



ACKNOWLEDGMENTS 



R. E. Morgan, V. Cornier, J. Sims, and 

 E. Rutledge assisted in field collections and 

 processing of specimens. R. E. Pearson helped 

 with the manuscript. V. E. Coleman prepared 

 the figures. 



LITERATURE CITED 



BAILEY, REEVE M., and CARL E, BOND. 

 1963. Four new species of freshwater scul- 

 pins, genus Cottus, from western North 

 America. Univ. Mich., Occas. Pap. 

 Mus. Zool. (634): 27 pp. 

 BRYANT, FLOYD C, and ZELL E. PARK- 

 HURST. 

 1950. Survey of the Columbia River and its 

 tributaries- -Part IV. Area III Washing- 

 ton streams from the Klickitat and Snake 

 Rivers to Grand Coulee Dam, with notes 

 on the Columbia and its tributarie s above 

 Grand Coulee Dam. U.S. Fish Wildl. 

 Serv., Spec. Sci. Rep. Fish. 37, 108 pp. 



17 



