LANDER and HENRY: 1965-66 BROOD COHO SALMON 



Table 3. — Values of F, m, Ni, N,., and N^/NQat various levels of natural mor- 

 tality for 1965-66 broods of marked Columbia River coho salmon {F is summed 

 for 4.5 mo, data from all hatcheries combined). 



Table 4. — Values of F, P, Ni, N^, and Nr/Nofor 1965-66 broods of marked coho 

 salmon from various Columbia River locations (F is summed for 4.5 mo; A/2 = 

 0.06). 



hatcheries from these four sections as well as 

 for the combined data for 12 M2 = 0.72 for the 

 1965-66 brood years, respectively. The quite 

 different results for the Middle River releases 

 are believed due primarily to the maxillary and 

 dorsal fins either regenerating or being over- 

 looked in the sampling (see footnote 2). Ignor- 

 ing the Middle River releases for the moment 

 and assuming that the effect of fin regeneration 

 or sampling equally affects the other marks, cer- 

 tain trends in the data are of interest. Thus, the 

 estimated proportion maturing (m) at age 2 

 consistently decreases from the Lower River to 

 the Uppermost River hatcheries for both brood 



years. In other words, these data suggest that 

 at the end of their second year, a greater por- 

 tion of the Lower River coho salmon matured as 

 jacks, and the proportion maturing as jacks 

 consistently decreased for coho salmon released 

 farther and farther upriver. 



Another statistic of interest in Table 4 is the 

 estimated proportion of released fish that sur- 

 vived to enter the fishery (Nr/No). The results 

 were not consistent for the two brood years in 

 that the Uppermost releases showed the highest 

 estimated recruitment to the fishery for the 

 1965 brood and lowest recruitment to the 

 fishery for the 1966 brood. However, in com- 



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