FEMALE SALMON (0. ncrka) OF THE COLUMBIA RIVER 



435 



Tablk 6. — Estimated egg potential of Okanogan blueback 

 salmon escapement itsing three methods of estimation, 1953 

 and l'J56-59 



[In millions of eggs] 



('orn|)an'(l witli otlicr years, regardless of the 

 influence of 1 -year-ocean fish. Tins indicates that 

 other factors also afl'ect the relationship. We iiave 

 sliown specifically, however, that the presence of 

 abnormal numbers of 1 -year-ocean females reduced 

 the egg potential of tlie 1953 Okanogan escape- 

 ment to a level well below that expected of a run 

 similar in size but normal in age and sex composi- 

 tion. Altliougii tlie impact of 1-year-ocean fe- 

 males would have been relatively less in terms of 

 the riverw'ide escapement, we feel that initial 

 overestimation of the egg potential accentuated 

 the poor escapement-return relationsiiip of 19.5:?- 

 57. It is evident that future analyses of tlie 

 Columbia River blueback escapement-return data 

 can be improved initially by refining the escape- 

 ment statistic with the added consideration of sex 

 ratio and age group fecundity. 



DISCUSSION 



Thus far, we have considered tiie effect of the 

 lower fecundity of 1-year-ocean fish on the egg 

 potential of a spawning stock and have pointed 

 out that, because of fluctuations in relative abun- 

 dance of 1-year-ocean fish in the escapement, the 

 egg potential is sometimes considerably less than 

 the number of spawners or even female spawners 

 indicates. It is appropriate to examine other 

 aspects of the occurrence of these 1-year-ocean fish 

 in the Columbia River blueback runs, including 

 their direct and indirect importance to the fishery 

 and the cause of their occurrence. 



Contribution of 3;*s to the Fishery 



Lack of sustained yearly information about the 

 composition of the escapement at Bonneville Dam 

 hinders efforts to calculate the exploitation rate 

 of the various age groups. The Oregon Fish Com- 



mission ' reports that in 1957 tiie fisher\ took 9 

 percent of the 82 age group as compared to 52 per- 

 cent of the 42 age group. The 32's thus contribute 

 Httle to the catch but are heavily represented in 

 the escapement. Their relative significance on 

 the Okanogan spawning grounds is further in- 

 creased by the fact that they return, almost 

 without exception, to that stream. By reason of 

 sheer abundance then, the Sa's often contribute 

 heavily to the egg potential of the Okanogan 

 escapement. Utihzing the number of female 

 spawners in each group and the appropriate 

 average fecundity of each age group, we calculate 

 that the So's contributed 88, 15, 14, 54, and 9 

 percent of the total egg potential for the years 

 1953, and 1956 through 1959, respectively. 



Because the S^'s are relatively invulnerable to 

 the gill net fishery as it is now conducted and, 

 therefore, contribute significantly to the repro- 

 ductive capacity- of the Okanogan escapements, 

 they might be considered as a safety factor in the 

 escapement to that river system. The apparent 

 advantages of such a feature would be nullified, 

 however, if the recurrence of the Sj's were genetic 

 in nature. For the Sa's to function beneficially 

 as a safety factor, they must be able to produce 

 catchable 42's as well as Sa's. Otherwise, the 

 contribution of the Okanogan River blueback pop- 

 ulations to the commercial fishery would, in time, 

 be eliminated. 



Age at Maturity — Genetic or Environmental? 



The question of whether age at maturity of 

 Pacific salmon is the result of environmental or 

 genetic influence or a combination of the two has 

 only recently attracted attention. Godfrey (1958) 

 working ^\•itll socke^e salmon at Rivers Inlet and 

 Skeena River, B.C. (Canada), concludes tiiat "age 

 at maturity is governed to a great extent by the 

 inheritance of certain genetic components of the 

 parents. Some environmental influence is a possi- 

 bility but must be proven." 



On the Deschutes River in Washington States 

 3-year-old chinook salmon {0. tshawijtscha) fe- 

 males were crossed with 2- and 3-year-old males, 

 separately to determine whether or not precocious 

 parents tend to produce precocious offspring 



> Westrhcim, S. J., and others. 1959. Columbia River investigations 

 progress report October 1957-Aprll 1958. Oregon Fish Commission (Port- 

 land), February, 1959, 54 p. Processed. 



