THOMAS: EVALUATION OF RETURN OF CHINOOK SALMON 



Table 4.-Potential egg production of adult chinook salmon returns in relation to 

 original egg numbers from which they were produced. 



Potential egg replacement of adult returns from 

 the various sources is shown in Table 4. The adult 

 return from the hatchery totaled 0.070%; however, 

 more than 40% of the adult fish returned as 2-yr- 

 old males. Only about 76% of the original eggs 

 were replaced for this brood year. Although the 

 percentage survival of hatchery fish was more 

 than four times that of channel fish, the advantage 

 in egg replacement was less than twofold. Even so, 

 a channel could not operate long with a less than 

 35% replacement of eggs. If adults from natural 

 spawning are assumed to enter the holding pond 

 at an equal ratio with those from the channel, 

 possible egg replacement from the creek source 

 was only about 7,000. 



The return of chinook salmon as 2-, 3-, and 4-yr- 

 old, and sometimes as 5- and 6-yr-old fish, ensures 

 overlapping of brood stocks. Consequently returns 

 from year classes with poor survival are mixed 

 with returns from other year classes, to help en- 

 sure that the hatcheries and streams may still 

 have adequate egg supplies. 



Production of salmon by incubation channels is 

 usually evaluated only by the number of out- 

 migrants produced and the total number of adults 

 that return. The origins and ages of adults are 

 seldom investigated. 



Only relative comparisons can be made of sur- 

 vival from channel and hatchery releases due to 

 variables such as time of release, size at release, 

 and nutritional background. The channel had the 

 sizable advantages of having very low costs for 

 rearing the fry and no cost for food. 



A 9-yr average of adult returns to the hatchery 

 was 0.118%. Survival to adults from the 1963 year 

 class of fish released by the hatchery was about 

 0.39%. There were no major differences in fish diet, 

 times of stocking, or other known factors that 

 might improve survival of this year class over that 

 of the 1964 year class. If it is assumed that sur- 

 vivals of fish from the channel follow the same 

 trends as do those from the hatchery, the more 



than fivefold greater hatchery returns for the 1963 

 year class would be reflected in channel production 

 returns. This would provide more than sufficient 

 egg production replacement. However, additional 

 studies are needed to confirm this survival as- 

 sumption. 



ACKNOWLEDGMENT 



I thank the staff of the Salmon-Cultural 

 Laboratory for their help in conducting this 

 experiment, and especially Laurie G. Fowler and 

 Joe L. Banks, for their help in identifying marked 

 salmon vertebrae and the Oregon Fish Commis- 

 sion's mark processing center which made the age 

 analysis from collected scales. 



LITERATURE CITED 



Gangmark, H. a., and R. D. Broad. 



1956. Further observations on stream survival of king salm- 

 on spawn. Calif. Fish Game 42:37-49. 

 Lister, D. B., and C. E. Walker. 



1966. The effect of flow control on freshwater survival of 

 chum, coho and chinook salmon in the Big Qualicum 

 River. Can. Fish Cult. 37:3-25. 

 TAIT, H. D., J. L. HOUT, AND F. V. Thorsteinson. 



1962. An evaluation of fyke trapping as a means of indexing 

 salmon escapements in turbid streams. U.S. Fish Wildl. 

 Serv., Spec. Sci. Rep. Fish. 428, 18 p. 

 Thomas, A. E., and J. M. Shelton. 



1968. Operation of Abernathy Channel for incubation of 

 salmon eggs. U.S. Bur. Sport Fish. Wildl., Tech. Pap. 23, 

 19 p. 



Weber, D. D., and G. J. Ridgway. 



1962. The deposition of tetracycline drugs in bones and 



scales of fish and its possible use for marking. Prog. 



Fish-Cult. 24:150-155. 

 Weber, D., and R. J. Wahle. 



1969. Effect of finclipping on survival of sockeye salmon 

 (Oncorhynchus nerka). J. Fish. Res. Board Can. 

 26:1263-1271. 



Worlund, D. D., R. J. Wahle, and P. D. Zimmer. 



1969. Contribution of Columbia River hatcheries to harvest 

 of fall chinook salmon (Oncorhynchia^ tshawytscha). U.S. 

 Fish Wildl. Serv., Fish. Bull. 67:361-391. 



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