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UBC Theses and Dissertations

The role of abandoned stream channels as over-wintering habitat for juvenile salmonids Brown, Thomas Gordon


The role of ephemeral swamps and intermittent tributaries (off-stream habitat) located on the flood-plain of a west coast Vancouver Island stream (Carnation Creek), as over-wintering habitat, was examined for two winters. All trout (Salmo gairdneri and S_. clarki clarki) and juvenile coho salmon (Oncorhynchus kisutch) off-stream habitat were identified and characterized. Within this habitat: seasonal movement of salmonids was noted, coho growth rates were measured, salmonid populations were enumerated and contribution of off-stream habitat to the total coho smolt production was estimated. Coho and trout did not occupy all winter flooded land. Trout occupied intermittent tributaries, while coho occupied both intermittent tributaries and ephemeral swamps. Salmonid use of flooded meadows was negligible. The contribution of off-stream habitat to the watershed's total smolt production was at least 23% and more than 15% came from sites devoid of water in summer. Seasonal movement of juvenile coho followed a distinct pattern and appeared dependent upon climatic conditions such as magnitude and timing of the first fall (Oct-Nov) freshet. Climatic conditions in spring (March-May) appeared to influence both growth and survival of coho within one small ephemeral swamp.

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