FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



273 



Table 26. — Percentage occurrence of various age groups in the random samples of seaward migrant 

 red salmon for the years 1925 to 1936, inclusive 



In considering the two major age groups, 3 and 4, it will be noted that the percentage 

 of the 4-year group decreases as the migration proceeds whde the percentage of the 

 3-year group increases. This phenomenon, while not so obvious because of the small 

 numbers in the samples, also appears to exist in the two minor age groups for the 

 percentage of the 5-year group decreases and the percentage of the 2-year group 

 increases as the migration proceeds. There is a tendency for the older age groups to 

 migrate earlier than the younger age groups. 



The average sizes of the seaward migrants hi the samples collected in the years 

 1925 to 1936, inclusive, are presented in table 27. There is a marked decrease, 

 especially among the 4-year migrants, in the average size during successive periods 

 of sampling. The decrease in size of the 3-year migrants would probably be more 

 apparent were it not for the fact that the fish are just commencing to grow at the 

 beginning of the migration period, and those fish which migrate late in the season 

 have grown a certain amount as indicated by two or tliree wide-spaced rings beyond 

 the winter check on their scales. Fish of the 4-year and 5-year groups seldom show 

 any new growth of the year until late in the migration period. 



From a study of the rate of growth of the fingerlings, as determined by their 

 scales, and from the above-mentioned data relating to the change in age composition 

 and size of the migrants during each year's seaward migration, the following trend of 

 events is indicated. Of the progeny of a given brood year, the fastest growing indi- 

 viduals (hence the largest) migrate to the ocean in the spring of their second year. In 

 the spring of the third year the largest individuals of the population left in the lake 



