7 GEORGE V SESSIONAL PAPER No. 38a tes A. 1917 
ON THE LIFE-HISTORY OF THE COHO. 
By C. McLean Fraser, Ph.D. 
Curator, Pacific Coast Biological Station, Departure Bay, B.C. 
(With Plates V, VI, and VII (7 figures), and figures (Graphs) 8, 9, 10, 11, 12, 18. 
The sockeye and the spring salmon, among the Pacific species, have received the 
monopoly of attention of investigators ever since the salmon trade became an important 
one on the Pacific coast, and naturally so, because these two species have been so 
important, commercially. In more recent years, on account of the scarcity of these 
at times, especially in certain localities, the other species have come more into 
prominence. The coho or silver salmon is now quite an important factor in the 
output of the canneries. In the cannery statements compiled for the Pacific Fisher- 
man Year Books it is shown that there has been a gradual though rapid increase in 
the coho pack in British Columbia until, for the year 1915, it amounted to 13 per 
cent of the whole output. It does not show as large a percentage for that year for 
the whole coast, but in 1912, when the sockeye pack was very low, it reached an 
amount over 10 per cent of the pack for the year. Besides those that are canned, 
an increasing number is being put in cold storage. As the importance of the coho 
is thus rapidly increasing it seemed worth while to take advantage of a situation 
somewhat favourable for learning something of the life-history of the species. 
Some work has already been done on the coho. It has been considered, along 
with other species, in papers on the Pacific salmon, in several papers by McMurrich 
und one by Gilbert. These deal largely with the age at maturity of the species. 
Some of the points touched on in these papers will be considered in connection with 
others that heretofore have not received special attention. 
The favourable conditions referred to are these: Coho spawn in a small creek 
that flows into the head of Departure bay, and in this creek, at all times of the year, 
the young coho may be seen. A locality for observation is thus very conveniently 
situated. After they have migrated, some of them must remain in the strait of 
Georgia throughout their lives in salt water, and possibly they all do, as they may 
be caught with hand lines throughout the greater part of the year. Various stages 
have been obtained from hand line fishermen in Departure bay. Through the kind- 
ness of Messrs. Broder, a large number of specimens of mature fish, a good repre- 
sentative lot for the strait, was examined at the cannery at Nanaimo. To compare 
with these, through the kindness of Manager Crawford, of the Neah Bay cannery, 
I was able to get a number from the open ocean. 
In the creek at Departure bay the mature coho appear about the middle of 
November. As the spawning beds are but a short distance up the stream, not more 
than a mile, they are soon reached, and the spawning is over by the end of the month. 
At the Cowichan Lake hatchery, where, until this season, the greatest number of 
ecohos in the province were hatched, the first eggs were taken about November 10, 
kut the spawning season lasts for a considerable time, as even after the first of 
February there are unspawned fish in the streams of the neighbourhood. 
The eggs hatch in three months, or slightly less, but the alevins remain buried 
in the coarse sand or fine gravel at some distance below the surface for some time. 
On March 7 not one could be seen in the creek, although the last year’s fry were 
39 
