HENRY: NATURAL AND FISHING MORTALITIES OF CHINOOK SALMON 



Table 3. — F, m, and R values for general marked fall chinook salmon of the 1962 

 brood; M is survival for 12 mo and F for 6 mo (adapted from Henry 1971). 



.30-, 



.20- 



.10- 



.002 



.004 



.006 



.008 



— I 

 .010 



Figure 2. — Relation between computed monthly natural mor- 

 tality (M,) during the first 18 mo after release as smolts emd 

 selected values of proportions of salmon maturing after 18 mo 

 imj) — 1961 brood of fall chinook salmon from Spring Creek 

 hatchery. 



the relation between M4, F3, and m^. As the m^ 

 value increases, F3 also increases and M^ de- 

 creases. It should be noted that for M4 values < 1.0 

 (summed over 12 mo), m^ must be well over 0.800. 



Although it is not possible to obtain unique es- 

 timates of the various parameters (only a range of 

 estimated values) by selecting either the M, or the 

 m,, the detailed relationships between the 

 parameters — based on selecting m, values — give 

 a very good insight into the effect of each of these 

 values on the other and the interrelationships be- 

 tween them. Furthermore, the graphic presenta- 

 tion of these relationships as shown in this paper 

 permit any assumptions about the various 

 parameters to be quickly examined. For example, 

 to obtain estimates of the various parameters 

 based on Cleaver's (1969) assumption that the M^ 

 ii = 2-4) are equal for the 1961 Spring Creek data, 

 we could go to Figure 5 and observe the m^ andFg 

 values for selected values of M^. 



Next, from Figure 4 for M4 = M3 = M^, and the 

 appropriate m^ values, we could calculate the 

 proper m2 and m-^ values. Then from Figure 3 for 

 these mj, m^, and m^ values we could determine 

 the proper Fj and F2 values and finally from Fig- 



t20n 



110- 



100- 



090- 



080- 



070- 



060- 



050- 



040- 



030- 



020- 



010- 



010 



.081 



200 



300 



400 



Figure 3. — Relations between certain computed monthly ocean 

 fishing mortalities (F,, F^) and selected values of proportions of 

 salmon maturing annually (m^, mj, m^) — 1961 brood of fall 

 chinook salmon from Spring Creek hatchery. 



ure 2, the correct estimate of Mj. Of course, any 

 other assumed relationships between the 

 parameters also can be examined readily from 

 these graphs. 



COMPARISON OF 1961 AND 1962 

 BROOD SPRING CREEK DATA 



I have selected the Spring Creek data to discuss 

 in this paper because in my earlier paper (Henry 

 1971) I stated, "It is unfortunate that no analysis 

 could be made for Spring Creek marks of the 1962 

 brood." This was due to the fact that there were no 

 fifth year recoveries recorded for the river (E^ =0), 



51 



