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RESTORATION OF STREAM PHYSICAL HABITAT AND FOOD RESOURCES: INFLUENCE ON JUVENILE COHO GROWTH AND SALMON DERIVED NUTRIENT INCORPORATION IN COASTAL OREGON STREAMS
Citation:
SHAFF, C. D. AND J. E. COMPTON. RESTORATION OF STREAM PHYSICAL HABITAT AND FOOD RESOURCES: INFLUENCE ON JUVENILE COHO GROWTH AND SALMON DERIVED NUTRIENT INCORPORATION IN COASTAL OREGON STREAMS. Presented at Oregon Chapter of the American Fisheries Society Meeting, Bend, OR, March 01 - 03, 2006.
Description:
ABSTRACT - Stream restoration in Western Oregon and Washington includes physical habitat improvement and salmon carcass additions. However, few studies examine the effects of carcass placement on juvenile fish in western Oregon, and in particular the interaction with physical habitat. Our goal was to explore how the placement of salmon carcasses and large wood affects juvenile coho salmon (Oncorhynchus kisutch) growth and salmon derived nutrient (SDN) incorporation. We studied three streams in the Coos Bay area with four treatment reaches per stream 1) reference, 2) wood placement, 3) wood placement + salmon carcass addition, and 4) salmon carcass addition. Growth was measured using PIT tagged coho salmon and SDN incorporation determined from 15N and 13C. We also conducted a survey of the incorporation of SDN in juvenile coho salmon across a range of natural and artificial spawner densities.
Growth of juvenile coho salmon was greatest in reaches with carcass additions alone. Wood placement had no impact of winter growth or condition. Our results may be limited to low winter flow conditions, since the winter of 2004 had unusually few storms. Along a gradient of spawner densities incorporation of SDN increased as natural spawner densities increased. We saw more incorporation of SDN from natural spawners than from placed carcasses indicating a difference in their function within the stream. Our results suggest that salmon carcass placement can improve juvenile coho salmon growth and condition under some stream conditions, and emphasizes the need for studies in a variety of stream conditions to assess the effects of stream restoration.