Steinhorst K.,University of Idaho |
Milks D.,Snake River Laboratory |
Naughton G.P.,University of Idaho |
Schuck M.,Snake River Laboratory |
Arnsberg B.,Nez Perce Tribe
Transactions of the American Fisheries Society | Year: 2010
Meeting escapement and recovery goals for Pacific salmon Oncorhynchus spp. is greatly facilitated by accurate and precise estimates of run size and stock composition. Although this is particularly important for endangered Pacific salmon runs like the Snake River fall Chinook salmon O. tshawytscha evolutionarily significant unit, few studies provide estimates with confidence intervals (CIs) and standard errors (SEs). We developed a run reconstruction method for fall Chinook salmon returning to Lower Granite Dam on the Snake River. We showed that composition estimates of fish returning to large river systems can be obtained through subsampling. The methods reported here yield CIs around those estimates. We used compound bootstrap methods to derive CIs and SEs on return numbers and composition. In general, if the number of fish returning for a group was 300 or more, we were 90% confident that our return estimate represented the true number within 10%. Estimates for smaller groups were generally imprecise. The analytical technique described here provides fishery managers with information necessary for assessing escapement and recovery goals and addressing conservation and harvest allocations of adult Snake River fall Chinook salmon. © by the American Fisheries Society 2010.
Rosenberger S.J.,Idaho Power Company |
Connor W.P.,U.S. Fish and Wildlife Service |
Peery C.A.,U.S. Fish and Wildlife Service |
Milks D.J.,Snake River Laboratory |
And 2 more authors.
North American Journal of Fisheries Management | Year: 2013
One form of prerelease acclimation of hatchery anadromous salmonid Oncorhynchus spp. juveniles is to truck the fish to remote points for extended holding at low densities in rearing vessels (e.g., tanks, raceways, or in-ground ponds) supplied with river water. We conducted a 3-year study to determine whether such acclimation enhanced the postrelease performance of hatchery fall Chinook Salmon O. tshawytscha subyearlings and reduced the potential for interaction with natural fall Chinook Salmon subyearlings. In comparison with hatchery subyearlings that were released directly into the lower Snake River just downstream of the acclimation facility, acclimated hatchery subyearlings (1) passed downstream to Lower Monumental Dam (the third dam encountered during seaward migration) faster, (2) passed the dam earlier, and (3) survived from release to the dam tailrace at higher rates. The differences in downstream passage rate and dam passage timing were also much greater between acclimated hatchery subyearlings and natural subyearlings than between directly released hatchery subyearlings and natural subyearlings. Thus, acclimation provided a survival advantage to the hatchery fish while reducing the potential for (1) aggressive and nonaggressive social interactions with natural fish while in transit through the reservoirs associated with Lower Granite, Little Goose, and Lower Monumental dams; and (2) confinement with natural fish at those three dams, where fish collection and raceway holding were followed by transport in tanker trucks. Our findings support acclimation as a method for enhancing postrelease performance of hatchery fall Chinook Salmon subyearlings and reducing their potential interactions with natural conspecifics. Received July 25, 2012; accepted January 9, 2013. © 2013 Copyright Taylor and Francis Group, LLC.