Age Structure and Hatchery Fraction of Elwha River Chinook Salmon: 2015 Carcass Survey Report
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Age Structure and Hatchery Fraction of Elwha River Chinook Salmon: 2015 Carcass Survey Report

Category: Fish/Shellfish Research and Management - Fish/Shellfish Research

Date Published: June 2016

Number of Pages: 27

Publication Number: FPA 16-04

Author(s): Josh Weinheimer, Joseph Anderson, Randy Cooper, Scott Williams, Mike McHenry, Patrick Crain, Sam Brenkman and Heidi Hugunin

This report summarizes the results from the juvenile monitoring study on the Duckabush River from 2011 to 2015. We evaluated freshwater productivity, juvenile outmigration timing, adult abundance and egg to migrant survival of summer and fall chum salmon. Abundance of adult summer chum was higher than fall chum four out of the 5 years of our study, and was composed almost entirely of natural-origin fish. Although we had no direct evidence, based on the exceedingly high survival rate needed to account for adult fall chum escapement from a single cohort monitored through the marine phase, we speculate that a significant number of fall chum spawners were stray hatchery origin fish from releases elsewhere within Hood Canal. Juvenile summer chum abundance ranged from three to twenty seven times larger than fall chum. Summer chum juveniles exhibited an earlier timed migration with peak outmigration occurring from late February to the middle of March. Egg to migrant survival for summer chum was higher than fall chum and was similar to values reported for other chum stocks on west coast. Fall chum egg to migrant survival was at the lower range of reported values for other fall chum stocks. Summer and fall chum freshwater survival appear to be negatively impacted by peak flow events and high spawning densities. Based on the results of this study, summer chum appear to be meeting the adult abundance and recruits per spawner recovery goals listed in the Summer Chum Salmon Conservation Initiative.