Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 239
Title: Coho salmon smolt production from constructed and natural floodplain habitats
Author: P. Roni, S. A. Morley, P. S. Garcia, C. Detrick, I. D King, E. M. Beamer
Publication Year: 2006
Journal: Transactions of the American Fisheries Society
Volume: 135
Issue: 5
Pages: 1398-1409

Abstract.We examined existing smolt trapping data from 30 constructed and natural floodplain habitats to determine whether the number (production), density, and length of coho salmon Oncorhynchus kisutch smolts varied by project type and area. At 13 of the 30 sites we conducted detailed physical surveys to examine how morphology (shoreline irregularity), depth, and cover influenced smolt density and length. Mean smolt production for all sites averaged 2,492, density 0.37 smolts/m2, and length 98.9 mm. We found no significant difference in smolt production or density between natural and constructed sites or among project types. Smolt length differed by project type and morphology, excavated ponds (gravel pits and mill ponds) producing significantly larger smolts than constructed groundwater or natural channels. Smolt production was positively correlated with wetted area. Smolt length was negatively correlated with density and distance from salt water, suggesting that sites further inland with cooler water temperatures had higher densities and smaller fish. Site perimeter, shoreline irregularity, depth, and percent cover were not significantly different among habitat types at intensively sampled sites, nor were they correlated with smolt production or smolt density. However, multiple regression analysis indicated that shoreline irregularity and percent cover explained 70% of the variation in smolt length.

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