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OVER-WINTER JUVENILE COHO SALMON GROWTH AND SURVIVAL IN A COASTAL OREGON STREAM NETWORK
Citation:
WIGINGTON JR, P. J., J. L. EBERSOLE, M. E. COLVIN, B. MILLER, B. HANSEN, H. LAVIGNE, J. P. BAKER, M. CHURCH, AND J. E. COMPTON. OVER-WINTER JUVENILE COHO SALMON GROWTH AND SURVIVAL IN A COASTAL OREGON STREAM NETWORK. Presented at American Fisheries Society, San Francisco, CA, September 02 - 06, 2007.
Description:
Winter habitat has the potential to be a limiting factor for the production and condition of coho salmon (Oncorhynchus kisutch) smolts, but little is known about how the variation of habitat throughout whole stream networks influences coho smolts. Over a four year period (2002 - 2006), we implanted > 20,000 juvenile coho salmon with passive integrated transponders (PIT) tags across the stream network of the West Fork Smith River, a 67 km2 drainage in coastal Oregon. We used mobile and stationary PIT tag antennae to track the locations of the tagged coho salmon within the stream network during the high-flow winter seasons (October - June). We trapped smolts leaving the drainage in a rotary screw trap, and we measured the lengths and weights of all PIT tagged coho salmon captured. We supplemented coho salmon captures at the smolt trap with selective seining and minnow trapping within the stream network. Smolt production from the stream network ranged from 15,949 to 38,971 during the four years, with the highest production occurring following a winter without severe hydrologic events. Coho salmon juveniles that over-wintered in perennial and intermittent tributaries accounted for a much greater proportion of PIT tagged coho captured at the smolt trap than coho salmon that over-wintered in mainstem habitats. We are currently developing hierarchical linear mixed effects models to estimate the influence of habitat at a range of scales on smolt production and size.