PNNL

Abstract

Survival studies of juvenile salmonids implanted with acoustic tags have been conducted at hydroelectric dams within the Federal Columbia River Power System (FCRPS) in the Columbia and Snake rivers between 2010 and 2014 to assess compliance with dam passage survival standards stipulated in the 2008 Biological Opinion (BiOp). For juvenile salmonids migrating downstream in the spring, dam passage survival defined as survival from the upstream dam face to the tailrace mixing zone must be =96% and for summer migrants, =93%, and estimated with a standard error =1.5% (i.e., 95% confidence interval of ±3%). A total of 29 compliance tests have been conducted at 6 of 8 FCRPS main-stem dams, using over 109,000 acoustic-tagged salmonid smolts. Of these 29 compliance studies, 23 met the survival standards and 26 met the precision requirements. Of the 6 dams evaluated to date, individual survival estimates range from 0.9597 to 0.9868 for yearling Chinook Salmon, 0.9534 to 0.9952 for steelhead, and 0.9076 to 0.9789 for subyearling Chinook Salmon. These investigations suggest the large capital investment over the last 20 years to improve juvenile salmon passage through the FCRPS dams has been beneficial.