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Combining Parentage Analysis with PIT-Based Estimates to Evaluate Stray Rates and Smolt-to-Adult Survival of Hatchery Coho Salmon <i>(O. kisutch)</i> Released from Multiple Sites within the Methow River Basin

Danielle Grundy, Katie Weber

Yakama Nation, 10 Piney Woods Rd, Twisp, WA 98856

The Methow River Basin, located in north central Washington, once supported 23,000 – 31,000 spawning coho salmon (Oncorhynchus kisutch).  By the early 1900s, these indigenous runs were decimated due to habitat degradation, improper harvest management practices, and the construction and operation of hydroelectric projects.  The Yakama Nation Fisheries Mid-Columbia Coho Reintroduction Program (MCCRP) is designed to promote tribal and recreational fishing opportunities as well as fulfill tribal salmon management objectives to develop a locally adapted, naturally spawning population.  Currently, the MCCRP releases hatchery coho from six acclimation ponds in addition to the onsite hatchery releases (Winthrop NFH).  To determine the efficacy of each of these sites, we utilize a PIT-based estimate of escapement combined with parentage analysis.  A portion of juveniles are PIT tagged prior to release and a portion of adults are tagged at Priest Dam.  The Dam Adult Branch Occupancy Model (DABOM) (Waterhouse, 2020) uses the detection of these PIT tags within the Columbia Basin to estimate the escapement of fish through the use of detection probabilities and movement probabilities past each interrogation site.  When incorporated with parentage analysis we can identify the effectiveness of each release location as well as stray rates within and outside the basin. Further studies of parentage analysis will allow us to identify the success rate of natural production through parentage analysis of natural-origin coho juveniles.