Survival of adult spring/summer Chinook salmon from the mouth of the Columbia River to Bonneville Dam, 2011

Accurate estimates of freshwater mortality from all sources are critical to fishery management decisions. However, aside from mortality attributed to harvest, the proportion of adult migrants lost through any mechanism between the river mouth and Bonneville Dam (rkm 234) had not been measured in a scientifically rigorous manner. In spring 2010 and 2011, we conducted a pilot study of adult survival from the mouth of the Columbia River to Bonneville Dam. During these two study years, we collected and tagged a total of 962 adult spring Chinook salmon and released them to the Columbia River estuary near river kilometer (rkm) 45. This report details work conducted in 2011, the second year of the pilot study. 2012 NMFS (National Marine Fisheries Service) NWFSC (Northwest Fisheries Science Center) Submitted Public Domain 1861