HENRY: FALL CHINOOK SALMON 



same as would be observed by reading along the 

 F3, F4, and F5 axes in Figures 13 and 14. It is 

 apparent from these data that at any level of 

 natural mortality (Mi), as fishing mortality is 

 increased on the 5-year-old fish (F5) (with Fs 

 and F4 = 0), total yield increases, although 

 slightly. For the Spring Creek data (Figure 

 15), any increase in F4, with the other two F 

 values = 0, would result in reduced yield. For 

 Kalama fish (Figure 16), for both broods at 

 M = 0.72 and higher, total yield would increase 

 with an increase in any of the F values. In gen- 

 eral, troll fishing on the age 3 and age 4 Spring 

 Creek and Kalama fall chinook salmon tends 

 to reduce total yield for Mi values less than 0.82, 

 except for the 1962 brood Spring Creek fish. 

 For these fish it appears that growth was in- 

 sufficient to compensate for natural mortality 

 losses of 4-year-old fish, even at a natural mor- 

 tality rate of If = 0.45. Thus, yield was in 

 creased by harvesting them as 3-year-olds in 

 the troll fishery (Fa). 



LITERATURE CITED 



Beverton, R. J. H., AND S. J. Holt, 



1957. On the dynamics of exploited fish popula- 

 tions. Fish. Invest. Min. Agr. Fish. Food (Gt. 

 Brit.), Ser. II 19, 553 p. 



Cleaver, F. C. 



1969. Effects of ocean fishing on 1961-brood fall 

 chinook salmon from Columbia River hatcheries. 

 Fish Comm. Oreg., Res. Rep. 1(1). 76 p. 



Henry, K. A. 



1971. Estimates of maturation and ocean mortal- 

 ity based on marked 1962-brood Columbia River 

 chinook salmon and effect of ocean fishing on the 

 total stock. Fish. Comm. Oreg., Res. Rep. 3:13-27. 



Lander, R. H. 



1970. Distribution in marine fisheries of marked 

 chinook salmon from the Columbia River Hatchery 

 Program, 1963-66. Fish Comm. Oreg., Res. Rep, 

 2(l):28-55. 



PULFORD, E. F. 



1970. Estimated contribution of Columbia River 

 hatchery fall chinook salmon to sport and com- 

 mercial fisheries in 1966. Fish Comm. Oreg., Res. 

 Rep. 2(1):3-14. 



Shapiro, A. P., and V. L. Andreev. 



1969. Optimal'noe sootnoshenie mezhdu iskusstven- 

 nym i estestvennym vosproizvodstvom oblavliva- 

 emoi populyatsii ryb (Optimum relationship be- 

 tween artificial and natural reproduction for 

 commercial populations of fishes). Vopr. Ikhtiol. 

 9(l):61-67. (Transl. in Probl. Ichthyol., 1970, 

 9(1) :45-49, issued by Am. Fish. Soc). 



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



1969. Contribution of Columbia River hatcheries to 

 harvest of fall chinook salmon (Oncorhynchus 

 tshawytscha) . U.S. Fish Wildl. Serv., Fish. Bull. 

 67:361-391. 



445 



