|Document Type:||Journal Article|
|Title:||Juvenile salmonid response to the replacement of engineered logjams (ELJS) in the Elwha River, Washington State, USA|
|Author:||G. R. Pess, Martin Liermann, M. L. McHenry, R. J. Peters, T. R. Bennett|
|Journal:||River Research and Applications|
Engineered log jams (ELJs) are increasingly being used in large rivers to create fish habitat and as an alternative to rip-rap for bank stabilization. However, there have been few studies that have systematically examined how juvenile salmonids utilized these structures relative to other available habitat. We examined Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), and trout (O. mykiss and O. clarki) response to the placement of engineered log jams (ELJs) in the Elwha River, Washington State, USA. We used summer snorkel surveys and a paired control-treatment design to determine how engineered logjams in a large river system affect the density of juvenile salmon. We hypothesized that densities of juvenile salmonids would be greater in habitats with ELJs than in habitats without ELJs in the Elwha River and that this ELJ effect would vary by species and size class. Juvenile salmonid density was higher in ELJ units for all control-treatment pairs except for one pair in 2002 and one pair in 2003. Positive mean differences in juvenile salmon densities between ELJ and non ELJ units were observed in two of four years for all juvenile salmon, trout greater than 100mm,, and juvenile Chinook salmon. Positive mean differences occurred in one of four years for juvenile coho salmon and trout less than 100mm. The results suggest that ELJs are potentially useful for restoring juvenile salmon habitat in the Elwha River, Washington State, U.S.A.