Contribution of Seasonally Flooded Lands and Minor Tributaries to the Production of Coho Salmon in Carnation Creek, British Columbia

Abstract

Ten percent of the juvenile coho salmon Oncorhynchus kisutch rearing in the main channel of Carnation Creek during the summer moved into intermittent tributaries and ephemeral swamps (off channel winter habitats) during the autumn of 1983. The number of juveniles residing within specific off channel sites during winter was governed by the magnitude of water levels associated with the first fall storms relative to the flooding levels required for adequate access to these sites (P < 0.05). Off channel habitats contributed 15.3% of the watershedˈs coho salmon smolts in 1983 and 23.1% in 1984. A 25-year flood event (65 m3/s) occurred in January 1984 and may have reduced the main-channel contribution for that year. The inability of coho salmon smolts to emigrate from off channel habitats and return to the main channel in spring may have reduced the off-channel contribution in 1983. April–May water levels were 37% below the 13-year mean water level in 1983 and 55% above it in 1984.