SALMON AND SALMON FISHERIES OF SWIFTSURE BANK 
783 
Of these latter recoveries, 15 were in the vicinity of Whidbey Island and in the Skagit 
River. These results would indicate that some individuals of the southern runs 
must either remain in the Gulf of Georgia during their life in salt water, or migrate 
inside of Vancouver Island on their return from the sea to the streams where they 
will spawn. 
AGE AT MATURITY 
Pritchard (1936) reported that commercially caught fish, secured for tagging 
experiments along the British Columbia coast during the years 1927-31, ranged in 
age from 2 to 4 years, but that 97.89 percent of these fish were in their third year. 
A small number of grilse, almost entirely precocious males, returned to the 
streams in the fall of their second year. Fraser (1920) reported that, of 2,000 cohoes 
examined from the Gulf of Georgia in 1916, all but 28 were in their third year, and 
that these 28 fish were all males in their second year. Gilbert (1912) reported a 
very few “sea-type” scales, from fish which have descended to salt water during 
then 1 first summer, in his collections from Puget Sound. Pritchard reported 0.35 
percent of this type of scale in his collections. 
It is reasonable to expect considerable fluctuations in the size of the runs of any 
species of which a high proportion of the individual fish mature at the same age. 
For those salmon which descend to salt water shortly after hatching, a considerable 
spawning escapement, combined with favorable conditions on the spawning grounds, 
often results in an extremely high return at maturity of that particular brood. 
That coho salmon, which mature almost entirely at 3 years of age, have not ex- 
perienced any sudden increase in numbers may be largely due to the fact that they 
have a long stream residence during their early life history. Because the carrying 
capacity of streams is physically limited, and there exists a considerable competition 
between the young stream-dwelling salmon and resident trout or other species, the 
numbers of fingerlings surviving until they begin their seaward migration cannot be 
increased beyond a certain point, even in very favorable years. Although this factor 
has doubtless had considerable influence in preventing large increases in numbers of 
coho salmon, the existence of so many populations in various streams has conversely 
aided in averting any sudden decrease in abundance, hence fluctuations in the 
numbers of this species have never been violent. 
INDIVIDUALITY OF POPULATIONS 
That the populations of different streams tend to be individual in nature is sup- 
ported by some experimental evidence. Gilbert (1913) reported the return in the 
fall of 1911 at Scotts Creek, California, of several coho salmon grilse from fingerlings 
marked there during the preceeding winter; no data as to returns of mature fish from 
this experiment were published. Fraser (1921) reported the recovery in Cowichan 
Bay, on October 11, 1917, of 1 coho salmon from 1,000 fry marked at the Cowichan 
Lake hatchery in March 1915. Pritchard (1936) reported the recovery in 1927 of 19 
adult cohos in Cultus Lake, B. C., from 72 fish marked there during the spring of 
the same year. These fish were in the early part of their third year when marked, 
and returned as adults after having remained only a few months in the sea. 
