be shown from tempering these fish for a short 

 time prior to release into water considerably 

 warmer than their acclimation temperature. It 

 was shown that the upper lethal temperatures 

 could be raised by several degrees if the fish 

 were acclimated at an intermediate tempera- 

 ture for a period of time. 



PROBLEMS AND SUGGESTED STUDIES 



In the development of the present study, 

 some insight has been gained with respect to 

 the problems stated in the initial proposal, 

 bur a number of additional problems have also 

 taken on importance. These problems will be 

 discussed in the present section, and the need 

 for future study with respect to various aspects 

 of these problems will be considered. 



Initial Problems 



At the outset of the present study, three 

 problems seemed of major importance. These 

 were: The relative survival of fry and finger- 

 ling releases, the relative contribution of 

 Spring Creek Hatchery stocks to the various 

 fisheries, and the magnitude of straying into 

 Spring Creek Hatchery. Additional work on 

 each of these problems is still required, but 

 scale studies and analysisof returns of marked 

 fish which are now in the ocean should be 

 sufficient. It should be pointed out, however, 

 that the problem of "relative contribution" 

 considered here is not intended to cover the 

 general problem of hatchery contribution which 

 will require a carefully planned program of 

 study involving all Columbia River hatcheries. 



Relative production of fry and fingerling 

 releases . — At the present time evidence from 

 regression studies and from experiments with 

 marked fish strongly suggests that the sur- 

 vival rate for fingerling releases greatly ex- 

 ceeds the survival rate for fry. A precise 

 estimate of the relative survival rates, how- 

 ever, must await returns of marked releases. 

 In order to rule out possible effects of mark- 

 ing, a scale study to determine a means of 

 identifying fry and fingerling releases as re- 

 turning adults would be of great value. 



Insofar as the 1956 Spring Brook fry were 

 released into near freezing water, returns 

 from the 1957 and 1958 broods, which were 

 also marked, should be studied. Whether or 

 not fry releases should be continued is a 

 separate problem needing careful considera- 

 tion. 



Contribution to fisheries . — Recoveries of 

 the 1959 marked returns to the Columbia 

 River indicated a high contribution to the gill 

 net fishery. This return involved only 3-year- 

 old fish, but marked returns in 1960, 1961, 

 and 1962 should be adequate to determine 

 precise estimates of the contribution to this 

 fishery. Ocean recoveries should supply some 

 information on the relative contribution to the 

 ocean troll and sport fisheries. Of course, if 

 the modal age has changed to 3 years, con- 

 tribution to ocean fisheries will be drastically 

 reduced. In this respect, the same situation 

 may be occurring at other Columbia River 

 hatcheries. A more thorough study of scales 

 to determine the age of adult returns at various 

 hatcheries is necessary. 



Straying. - - Although straying of marked fish 

 from other sources has been observed at 

 Spring Creek Hatchery, quite a few marked 

 Spring Creek Hatchery releases have been 

 taken in other areas. It is therefore indicated 

 that straying from, as well as to. Spring Creek 

 Hatchery should be investigated. Marked re- 

 turns of Spring Creek Hatchery releases 

 should be available in the next 2 or 3 years, 

 and data on returns to Spring Creek Hatchery 

 of marked fish from other sources should be 

 sufficient for such a study. In studying stray- 

 ing to Spring Creek care should be taken to 

 eliminate any releases of marked fish which 

 could be considered as transplants, because 

 straying has generally been observed under 

 such conditions (Ricker, 1959; see footnote 12). 

 Our preliminary studies of scales taken at 

 Spring Creek indicate that an intensive scale 

 study might be of value in estimating the ex- 

 tent of straying. 



Additional Problems 



Reduction in productivity . — It is obviously 

 beyond the scope of the present study to 



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