Improving Chum salmon escapement assessments for Grays Harbor, WA

Since 2015, the Washington Department of Fish and Wildlife (WDFW) has been working to improve Chum escapement estimates resulting in two technical reports (Edwards and Zimmerman 2018; Ronne et al. 2019). Previous work assessed distribution inside versus outside index reaches, area-under-the-curve estimates within index reaches, carcass tagging estimates of abundance in select index reaches, estimates of spawner stream life duration, and total spawner abundance of Chum salmon within tributaries of Grays Harbor. This proposal seeks to further implement an accurate and precise method for estimating escapement of Chum in sub-basins yet to be evaluated. Utilizing new methods, we also seek to revise run size estimates of historical abundance. This methodology can be used in other systems throughout the area covered by the Pacific Salmon Treaty. Current escapement estimates in Puget Sound and coastal Washington are derived from methods developed in the 1970s with the understanding that those methods were based on unsubstantiated assumptions that would later be revisited and refined. Over 40 years later, those methods are still being used for escapement estimates. Chum have become a constraining stock on the Grays Harbor salmon fisheries. Therefore, refined Chum assessments may alter management strategies moving forward.