Juvenile Salmonid Monitoring Following Removal of Condit Dam in the White Salmon River Watershed, Washington, 2017

Abstract

Condit Dam, at river kilometer 5.3 on the White Salmon River, Washington, was breached in 2011, and removed completely in 2012, providing anadromous salmonids with the opportunity to recolonize habitat blocked for nearly 100 years. Prior to dam removal, a multi- agency workgroup concluded that the preferred salmonid restoration alternative was to allow natural recolonization. Monitoring would assess fish recolonization efficacy, followed by management evaluation 5 years after dam removal. Limited monitoring of salmon and steelhead recolonization has occurred since 2011. The U.S. Geological Survey began juvenile salmonid monitoring in 2016 and did a second year during 2017, with sampling efforts like those of 2016. River conditions differed between the 2 years, both during (that is, high flows in 2017) and prior to (that is, 2015 summer drought conditions and December 2015 White Salmon River flood event) sampling. We operated a rotary screw trap at river kilometer 2.3 (3 kilometers downstream of the former dam site) from early April through early June to assess species diversity, and production of smolt and other migrant life stages. We also used backpack electrofishing during summer to assess juvenile salmonid distribution and abundance. Both sampling methods provided the opportunity to collect genetic samples (analysis of samples was not covered under funding received from the Mid-Columbia Fisheries Enhancement Group for the 2017 monitoring efforts) and to tag fish with passive integrated transponder (PIT) tags, which will provide life-history data through future recaptures and detections. The screw trap captured steelhead (anadromous rainbow trout, Oncorhynchus mykiss), fry, parr, and smolts; coho salmon (O. kisutch) fry, parr, and smolts; and Chinook salmon (O. tshwaytscha) fry, parr, and one smolt. Prolonged high water and some missed trapping periods during 2017 prevented us from generating smolt estimates. Despite difficult trapping conditions, the number of coho salmon fry and parr, and steelhead fry and parr captured in 2017 exceeded those captured during 2016. The number of age-0 Chinook salmon captured in the screw trap during 2017 was much higher (n = 222) than in 2016 (n = 4)