FACTORS INFLUENCING THE RETURN OF 



FALL CHINOOK SALMON (Oncorhynchus tshawytscha) 



TO SPRING CREEK HATCHERY 



by 



Charles O. Junge, Jr., Research Assistant Professor 

 Lloyd A. Phinney, Fishery Aide 

 Fisheries Research Institute, College of Fisheries 

 University of Washington, Seattle, Washington 



ABSTRACT 



This preliminary study is primarily concerned with a definition of the problems 

 that must be considered in isolating the factors influencing the relatively high sur- 

 vival rates of chinook salmon (Oncorhynchus tshawytscha) at Spring Creek Hatchery, 

 Washington, The tabulation and study of basic data relating to the distribution of egg 

 take, releases of fry and fingerlings, and adult returns were the first steps in this 

 analysis. 



An index of production based on female returns adjusted for the effects of the 

 Columbia River gill net fishery was related to the releases of fry and fingerlings 

 which had been spawned 4 years earlier. Returns for the brood years 1941-49 were 

 first investigated, since construction completed for the 1950 brood altered the 

 available facilities at Spring Creek Hatchery. A multiple correlation coefficient of 

 0.891 (P<0.01) gave indication of a reasonably consistent relationship between 

 releases of fry and fingerlings (in pounds) and subsequent returns. A correlation of 

 0.890 between r-eturns and fingerling releases only gave strong evidence that varia- 

 tions in return were controlled almost entirely by fingerling releases. Some qualifi- 

 cation of this result is necessary since in 1948 and 1949 at the time when large 

 numbers of fry were released into the Columbia River, water temperatures in the 

 river were near freezing in contrast to the constant temperature of 46° F. of Spring 

 Creek water. It is highly probable that such a temperature differential could induce 

 mortalities. 



When the study is extended to more recent years it is apparent that survival 

 rates since 1950 have been greatly reduced. When the pounds of fingerlings released 

 are taken into consideration, even the large returns in 1958 and 1959 do not exhibit 

 survival rates comparable to those maintained in the 1940's. Factors coincident 

 with this reduction are considered — incidence of tuberculosis and coagulated yolk 

 disease, increased crowding of fingerlings, and change in diet. 



In light of the findings of the present study, additional studies are proposed. 



INTRODUCTION town of Underwood, Wash., is primarily con- 



cerned with the production of fall chinook 

 Spring Creek Hatchery, a Federal installa- salmon (Oncorhynchus tshawytscha) although 

 tion located on the Columbia River near the other salmonids are included in the operations 



from time to time. The Spring Creek chinook 



— :; ~ — ; — _, _ ^ . jf r-. u • run was originally developed from eggs taken 



Note.--Charles O. Junge, Jr. resigned from Fisheries ^ „. „„^ ^ , „. _, °° 



Research Institute. November 1961. Lloyd A. Phinney ^^om Big White Salmon River, and a substantial 



now with Washington State Department of Fisheries. run of fall chinook now returns to Spring Creek 



