COHO SALMON (ONCORHYNCHUS-KISUTCH) USE OF LAKES AND STREAMS IN THE KEOGH RIVER DRAINAGE, BRITISH-COLUMBIA

Seasonal patterns of freshwater habitat use by coho salmon were docume nted in two small watersheds on northern Vancouver Island over a three -year period to assess the importance of small lakes and non-natal tri butaries as rearing and as rearing and over-wintering areas. Spawning occurred at a limited number of locations in these systems. Newly-emer ged coho fry moved both upstream and downstream from spawning areas in the Misty Lake system towards Misty Lake. The capture of fry in Long Lake and its outlet stream, where spawning was not observed, indicated upstream dispersion of fry from the Keogh River. The lakes provided b oth summer rearing and over-wintering habitat for juvenile coho salmon , but their use varied between years. The mainstem Keogh River was use d in primarily for rearing during summer. Coho fry generally grew fast est in the lakes and their outlet streams. Cohorts of large fry (mean FL > 80 mm) did not show over-winter growth, but the mean sizes of coh orts of small fry (mean FL < 70 mm) increased over winter, suggesting size-differential mortality. The utilization of small tributary lakes and streams as both summer rearing and over-wintering habitat by juven ile coho salmon suggests that more emphasis should be placed on the pr eservation and management of such areas. Because use of these habitats may be temporally variable, their importance is easily underestimated .