suggest detailed experiments dealing with the 

 highly specialized problems of disease, nutri- 

 tion, rearing density, genetics, etc. We strongly 

 suggest, however, that a centralized program 

 involving specialists in the related fields be 

 inaugurated for the study and control of such 

 factors. We recognize that much basic work is 

 progressing in these fields, but a centralized 

 program could coordinate the study of inter- 

 related factors and assure the application of 

 the best known procedures at each hatchery. 



Some suggestions of a nontechnical nature 

 may be given. For example, it has been pro- 

 posed that the pasteurization of all salmon 

 products used in hatchery diets may reduce the 

 incidence of infection with acid-fast bacteria; 

 but, considering the extent of infection through- 

 out the Columbia River hatcheries, a continua- 

 tion of work on this disease is necessary. 

 There are strong indications, however, that 

 other factors are affecting survival. The cause 

 of coagulated yolk disease is unknown, and the 

 possibility that it may influence eventual sur- 

 vival cannot be ruled out. The need for in- 

 creased study of this disease is apparent. 

 Also, indications of the present study suggest 

 that specialists should examine the changes in 

 rearing densities and diet that have occurred 

 at Spring Creek Hatchery in the last 10 years 

 and begin pertinent studies. We strongly rec- 

 ommended that the handling of fingerlings at 

 the time of release be eliminated since rela- 

 tively inexpensive devices are now available 

 for counting fish with adequate precision. 

 Little work should be required to evaluate the 

 use of such devices at hatcheries. 



Relationship between problems at Spring 

 Creek Hatchery and problems at other hatch- 

 eries . — A major purpose for the study of 

 Spring Creek Hatchery is to determine means 

 of increasing production at other Columbia 

 River hatcheries; therefore, the need for a 

 vomparative study of other hatcheries is 

 obvious. For such a study adequate data on 

 releases and returns must be available. The 

 Little White Salmon Hatchery and Willard 

 Hatchery located on the Little White Salmon 

 River should satisfy this condition, and we 

 suggest that a study, similar to the present 

 Spring Creek Hatchery study, be made of this 

 hatchery as well as other suitable hatcheries; 



Apparent change in modal age of maturity . — 

 It is unfortunate that for the present investi- 

 gation it is necessary to base an analysis of 

 age of return on assumptions involving length 

 measurements of adults returning to another 

 hatchery and length measurements at Spring 

 Creek Hatchery for a single year, 1959. Scales 

 were taken in conjunction with length measure- 

 ments, but reading of scales has been incom- 

 plete and fragmentary. Preliminary study 

 indicates that Spring Creek scales are easily 

 read for age, and the need for prompt reading 

 of these and scales from fish of the 1960 re- 

 turns is apparent. Some problems in reading 

 scales from adults returning to the Little 

 White Salmon Hatchery have been observed, 

 but the use of scales from marked returns 

 should be sufficient to solve these problems. 

 Excellent sampling techniques have been de- 

 veloped by Anders" for the 1959 return at 

 Spring Creek Hatchery, and we suggest that 

 these methods be standardized for general 

 use. In view of the effect of age of return on 

 the relative contribution to ocean fisheries, 

 the determination of the age composition in the 

 Columbia River as well as at a number of 

 hatcheries is important. If the present sampling 

 of the gill net fishery is supplemented by 

 sampling at Bonneville Dam, this should be 

 possible. 



Disposition of eggs . — Centralized planning is 

 important not only for rearing techniques but 

 also for determination of the most efficient 

 disposition of the eggs taken, i.e., that dis- 

 position which in the long run will result in the 

 largest production of adult salmon. In 1958 

 over 80 million eggs were collected from fish 

 returning to Spring Creek. Of these, less than 

 8 million were reared at Spring Creek Hatch- 

 ery. Less than 6 million were released as 

 unfed fry. The remaining 66 million were dis- 

 tributed among other Columbia River hatch- 

 eries (appendix table 1). Some releases of 

 marked fish have shown survival rates to 

 adulthood in the vicinity of one-half of 1 per- 

 cent, and it is very likely that fingerling 

 releases in the 1940's experienced such a 

 survival rate. Such a survival rate on 80 mil- 

 lion eggs would produce more adult salmon 



" Floyd Anders. Bureau of Commercial Fisheries, 

 unpublished manuscript. 



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