Survival and Traits of Reconditioned Kelt Steelhead Oncorhynchus mykissin the Yakima River, Washington

We evaluated the traits and survival to release of reconditioned kelt steelhead Oncorhynchus mykissin the Yakima River (Washington State, USA). From 2001 to 2011, we captured a total of 9,738 downstream-migrating kelts at an irrigation diversion facility, an average about 27% of each annual wild steelhead return. Captured kelts were reared for 4.5–10 months in an artificial environment, treated for diseases and parasites, and fed both krill and pellets. Surviving reconditioned fish were released into the Yakima River during the peak of the upstream migration of prespawn steelhead. Reconditioned steelhead kelts were predominantly (>92%) female. Annual survival to release ranged from 20% to 62% and averaged 38% over the course of the study, the surviving reconditioned kelts showing increases in FL, weight, and Fulton's K condition factor compared with their preconditioning status. Kelts in good condition and those with bright coloration at the time of collection were more likely to survive than those of poorer status at collection. Postrelease timing of upstream migration by reconditioned kelts was spread over several months and correlated well with the run timing of prespawn migrants upstream. The empirical results we observed demonstrate the potential for kelt reconditioning to provide recovery benefits for repeat spawning imperiled wild populations in highly developed river systems. Received July 17, 2012; accepted March 15, 2013