AGE AT MATURITY OF THE PACIFIC COAST SALMON 
9 
cases this may be the source of genuine doubt as to the early history of the individual 
and incidentally as to its age. For, if the nuclear narrowing be interpreted as indicat- 
ing the first year spent in fresh water, the age will be greater by one year than if it be 
interpreted as the central narrowing of a large nuclear area of the “sea type.” It is 
believed, however, that all doubt of this character can be removed by further investi- 
gation. For purposes of a preliminary discussion, like the present, as the doubtful 
cases are few in number, they can be omitted from consideration. 
There is a fair indication — not to be taken as conclusive — that those individuals 
among the sockeyes which proceed to sea shortly after attaining the free swimming 
stage experience a mortality far in excess of those which pass to sea as yearlings, but 
that those of the first class which survive grow much more rapidly the first year than they 
would have done had they remained in fresh water. To a certain extent they seem to 
maintain this preponderance in size during succeeding years. In the Fraser River, as 
already indicated, only a very small proportion of adult fish have developed from young 
which sought the sea during their first year. Thus out of 625 individuals taken at 
random, without selection, from the cannery floor, only 35 belong to this group, while 
590 had spent their first year in their native waters. So limited a number as 35 forms a 
wholly inadequate basis for generalizations, but it is worthy of note that 3 of these 
were grilse, maturing in their third year, 30 were in their fourth year, and only 2 in their 
fifth. If a larger series shall verify essentially the proportions here indicated it will 
demonstrate that early migration of the young accelerates growth and also the early 
coming to maturity, producing a larger proportion of grilse which mature in their third 
year, and a much greater preponderance of fourth to fifth year fish than occurs among 
those which migrate as yearlings. The increased size at the same age becomes evident 
on comparing the three “sea type” grilse above mentioned with “stream” grilse taken 
on the same date. The former were respectively 23, 23^, 23^4 inches long and weighed 
4^ to 5^ pounds. Sixteen grilse of the stream type taken on the same date (all that 
were secured) show the following lengths in inches: 17^, 18, 18, 18^, 18%, i8)4, 
18^, 19, 19, 19^, 19^4, 19 / 4 , 19 / 4 , 20, 20^. Three of these, i 8 } 4 , i 8 } 4 , and 19^^ 
inches long weighed each 2^ pounds. It is further noticeable that 2 of the 3 grilse of 
the sea type were females, while among Fraser River grilse of the stream type females 
are so rare that we have thus far discovered but one among over a hundred grilse 
examined. This is a matter, however, which may be subject to wide variation in dif- 
ferent streams. In the Columbia River, for instance, in 1910, grilse were numerous, and 
males and females in approximately equal numbers. 
In discussing the commercial value of a run the grilse may be omitted from con- 
sideration, as ordinarily they are few in number and so small as to have practically no 
value. The valuable elements of the run are fish which are maturing in their fourth or 
in their fifth years. It was attempted during the season of 1911 to determine the rela- 
tive proportions of these two generations, their range in size, and their average weight. 
In order to simplify the problem as much as possible we have omitted from our list the 
comparatively few individuals of sea type. In 500 fish of stream type, taken at ran- 
dom from the cannery floor, 271 were 4-year and 229 5-year fish. Of the 271 4-year 
