Transportation of Steelhead Kelts to Increase Iteroparity in the Columbia and Snake Rivers

Abstract

We tested the feasibility of transporting steelhead Oncorhynchus mykiss kelts (postspawned adults) around hydroelectric dams on the Snake and Columbia rivers to increase the returns of repeat spawners. Altogether, 5,878 kelts were collected, tagged with passive integrated transponder tags, and assigned to transported or in-river treatment groups at Lower Granite Dam (n = 5,320 [2002–2004]) on the Snake River and John Day Dam (n = 558 [2002]) on the Columbia River. Returns of repeat spawners differed by site and year: 11.1% (62/558) for the John Day Dam sample and 1.4% (27/1,959), 0.5% (6/1,241), and 0.8% (17/2,120) for the Lower Granite Dam samples in 2002, 2003, and 2004, respectively. Transportation tests indicated that kelts transported from the Snake River were approximately 2.3 times more likely to return than fish allowed to migrate in-river. Transport benefits were greatest for wild-origin female kelts, a demographic with high conservation value. There was no significant benefit for kelts transported from John Day Dam, although transported fish returned at a slighter higher rate (1.1 times). Comparisons between treatment groups (in-river versus transport) and locations (Snake River versus Columbia River) indicated that the greatest potential transport benefit may be for Snake River kelts owing to the population's low overall iteroparity rate and numerous potential kelt collection sites. The small sample sizes of returning fish limited our ability to examine more complex trends and environmental effects on return rates. Additional research is needed to fully evaluate the efficacy of kelt transportation in the context of regional steelhead recovery efforts.