Estimates of Escapement for Wind River Coho Salmon, 2007 – 2015

The Lower Columbia River (LCR) coho salmon Evolutionary Significant Unit (ESU) is composed of 24 distinct independent populations (DIP) split between three Major Population Groups (MPG) that are located in the states of Washington and Oregon. The Wind River watershed, which enters the Columbia River nine miles upstream of the Bonneville Dam, is part of the Upper Gorge DIP and Gorge MPG. Until the removal of Condit Dam on the White Salmon River in 2011, the Wind River basin contained the majority of habitat for coho salmon in the Upper Gorge DIP. Beginning in 2007, the Washington Department of Fish and Wildlife has conducted annual spawning ground surveys for adult coho salmon in the Wind River basin. The objectives of these surveys were to monitor Viable Salmon Population (VSP) parameters, including abundance, the proportions of hatchery-origin spawners (pHOS), sex ratio(proportion female spawners), and spatial distribution. Over the past nine years (2007 - 2015), the adult coho salmon spawner abundance (i.e., escapement) in the Wind River watershed has ranged from 28 to 92. Despite no hatchery releases in the Wind River, the median pHOS among years was 25%, leading to estimates of natural-origin escapement ranging from 21 to 70. Across all years, the median sex ratio was 55% females and ranged from 51 - 60%. Coho salmon are restricted to <10% of the total spawning and rearing habitat within the Wind River watershed, largely due to a natural-barrier falls located in the lower river. Within the accessible habitat reaches, coho spawn in both the Little Wind River, which is a tributary of main stem, as well as the main stem Wind River. Overall, the Wind River watershed consists of a relatively small sub-population of coho salmon due to limited and low quality habitat. Moving forward, it should be a priority to initiate adult coho monitoring in the White Salmon watershed that, along with Wind River monitoring, will allow for a more complete Upper Gorge DIP group abundance estimate.