198 Shelby D. Gerking 



Classifying the salmon on the basis of the same freshwater age 

 but different ocean age, Rounsefell pointed out that the older 

 salmon produced a significantly smaller number of eggs than 

 younger ones. The average for the former was 2,987 per 

 female and the average for the latter was 3,285, based on 

 about 150 specimens in each group. The difference in fecund- 

 ity for sockeye with identical ocean histories but different 

 freshwater ages also favoured the idea that age has an effect 

 on salmon fecundity since the older females produced 118 

 fewer eggs than the younger ones. The difference was not 

 statistically significant and the data were more variable. The 

 increased variation was explained by the variable freshwater 

 environment as opposed to more stable ocean conditions. 



Rounsefell reviews the literature of the fecundity of the 

 family Salmonidae, and of primary interest here is his demon- 

 stration that generally the rate of increase in number of eggs 

 declines as the fish increase in size. This may indicate that age 

 influences egg production, or it may be simply a description of 

 the way in which the ovary grows in relation to the rest of the 

 body. It does explain, however, why trout hatcheries discard 

 their old brood stock. The number of eggs in relation to the 

 weight of the fish declines as the fish increase in size, and it is to 

 the hatchery's advantage to have on hand a greater number of 

 smaller breeders than an equal weight of older ones. 



Haddock. One of the most penetrating analyses on the 

 effect of age on the fecundity of egg-laying fishes has been 

 done by Raitt (1933). He was also influenced by Orton's 

 writings. The mature eggs of 169 haddock {Melanogrammus 

 aeglefinis) of Scottish waters were counted and fecundity was 

 related to length, weight, and age. Four main comparisons 

 were made: (1) rate of increase in fecundity with length, 

 (2) rate of increase in ovary weight with length, (3) rate of 

 decrease in body weight in relation to length during ovarian 

 development, and (4) rate of increase in body weight with 

 length. Comparison of these relationships indicated that 

 fecundity increases with age up to age V, but at older ages 



