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ABSTRACT Releasing fish at varied life stages is an underutilized hatchery‐rearing practice. Columbia River Treaty tribes have been working to reintroduce extirpated Coho Salmon to historical habitats in upper watersheds. This effort has included the release of hatchery‐origin fish at both the parr and smolt life stages in the Yakima River Basin (Washington State USA), a tributary to the Columbia River. We evaluated releases of parr and smolts tagged with passive integrated transponders over 11 brood years. We assessed emigration timing, fish survival, and age‐at‐return for the two release groups. Emigrating juveniles released as smolts had higher survival and arrivedmore » downstream earlier than fish released as parr. Survival from release locations to adult return did not significantly differ for the two release groups. However, we observed a difference in apparent marine survival as fish released as parr had mean juvenile‐to‐adult return rates greater than fish released as smolts. Parr releases also tended to return at older age than smolt releases. Our results indicate that implementing practices to reduce homogenization of hatchery releases may produce survival and diversity benefits as fish mature to later life stages. Given the rapid ecosystem changes Pacific Salmon are experiencing throughout their life cycles, practices such as this may have increasing utility and import.« less

Abstract Steelhead Oncorhynchus mykiss are iteroparous, distinguishing them from Pacific salmon Oncorhynchus spp. that are semelparous. In this study we evaluated enhancement techniques that exploit this life history strategy to facilitate species restoration and recovery. In the Columbia River basin, where the natural ecosystem has been substantially altered over several decades due to human influence, all steelhead populations are listed as threatened or endangered under the U.S. Endangered Species Act. One factor believed to be limiting survival of Columbia River kelt (postspawned) steelhead is poor migration success to the ocean past several dams. We evaluated three treatments for kelts capturedmore » in the Yakima River basin from 2002 to 2011: (1) transport and release below Bonneville Dam (to provide unimpeded access to the ocean); (2) short-term reconditioning (holding and feeding in an artificial environment to facilitate gonad maturation) with transport; and (3) long-term reconditioning. These treatments were compared with an in-river migration control group to identify differences in the rate at which kelts survived and returned to Prosser Dam for potential repeat spawning (hereafter repeat spawners). The long-term reconditioning treatment exhibited the highest return rate of repeat spawners (range, 11.5–17.6%). The short-term reconditioning treatment with transport downstream from Bonneville Dam had a 3.2% return rate. The transport only treatment exhibited the lowest return rate (0.9%); this was only one-third of the control group's return rate (2.7%). Our results indicate that long-term steelhead kelt reconditioning is more successful than either transportation or in-river migration alternatives at increasing potential repeat spawner abundance and providing recovery benefits in river systems that have experienced substantial losses in natural productivity due to loss of habitat and habitat connectivity. Received June 23, 2015; accepted February 27, 2016 Published online July 15, 2016« less