Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8769
Title: Relocation and recolonization of coho salmon Oncorhynchus kisutch in two tributaries to the Elwha River:  implications for management and monitoring
Author: Martin Liermann, G. R. Pess, M. McHenry, John R. McMillan, Mel Elofson, T. R. Bennett, Raymond Moses
Publication Year: 2017
Journal: Transactions of the American Fisheries Society
Keywords: coho salmon,dams,recolonization,life history diversity,coho salmon,dams,recolonization,life history diversity

In 2012 the lower of two Elwha River dams was breached, restoring access of anadromous salmonids to the middle Elwha Rver (between the two dams), including two distinct tributaries:  Indian Creek and Little River.  While comparable in size, Indian Creek is considerably less steep than Little River (mean slope 1.0 vs. 3.5%), and has a warmer stream temperature regime due to its source, Lake Sutherland.  During and after breaching, coho salmon Oncorhynchus kisutch was relocated to these tributaries from the lower Elwha River hatcheries (below the dams) to determine if individuals from a hatchery-dominated population would successfully spawn and seed the systems with juveniles, and to assess differences in recolonization between the streams.  Transplantation led to immediate spawning, which resulted in smolt migrants per stream km comparable to other established coho salmon populations in the Pacific Northwest.  During the first 2 years of the relocation, redd densities in the two systems were similar, but Indian Creek produced four to five times as many smolts per km as Little River.  In addition fry migration occurred two to 4 weeks earlier in Indian creek, as predicted by the warmer incubation temperatures.  In the first years of the study there was little evidence of natural colonization of the two tributaries by adults.  However, in 2016, over half of the observed adults returning to the two tributaries were not transplanted, suggesting that progeny from transplanted fish were returning to their natal waters.  This work demonstrates that transplanting hatchery dominated coho salmon adults into newly available habitat can result in immediate freshwater production that is comparable to other systems and that density and timing of juvenile migrants can differ dramatically based on the seeded habitat.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize the interaction of human use and habitat distribution, quantity and quality.
Characterize the interaction of human use and habitat distribution, quantity and quality.