|Document Type:||Journal Article|
|Title:||Coastal distribution and consequent factors influencing production of endangered Snake River sockeye Salmon|
|Author:||S. Tucker, M. E. Thiess, J. F.T. Morris, D. L. Mackas, W. T. Peterson, J. R. Candy, T. D. Beacham, Eric Iwamoto, David J. Teel, Marc Trudel|
|Journal:||Transactions of the American Fisheries Society|
|Keywords:||sockeye salmon,Snake River,marine ecology|
Snake River sockeye salmon (Oncorhynchus nerka) was declared endangered in 1991 following several years of decreasing abundance. Several factors likely contributed to the decline of Snake River sockeye salmon, including poor marine survival. Little is known about the migration and ocean distribution and factors influencing production. We sampled coastal waters in June-July, October-November, and February-March from southern British Columbia to southeast Alaska 1998-2011 and in May-June and September from Oregon to Washington 2007-2010. A total of 8227 juvenile sockeye salmon were captured. Despite extremely low abundance relative to other stocks, 15 coded-wire tagged juvenile Snake River sockeye salmon from Redfish Lake have been recovered primarily off the coast of British of Columbia in spring and summer surveys since 2007. DNA analyses revealed an additional 8 juvenile Redfish Lake sockeye salmon also present in this area during summer. Snake River smolts undertook a rapid northward migration that brought them well beyond the Columbia River estuary and plume to expose them to ocean conditions prevailing off British Columbia. Through a multi-model inference approach, we characterized associations between the number of returning adults and a suite of ocean and river variables. Seven ocean and five river variables were chosen for the model selection analysis including copepod anomalies, coastal upwelling, date of spring transition, river discharge, river temperature as well as the proportion of smolts transported through the hydrosystem. While adult return was highly correlated to smolt abundance, our analyses suggests that ocean conditions encountered in the first growing season, as indexed by copepod biomass anomalies, contribute to the variability in total adult returns. There was also evidence for a negative effect of transporting smolts through the hydrosystem with the caveat we are using transportation data for steelhead trout (O. mykiss) as a proxy.
|Theme:||Recovery, Rebuilding and Sustainability of Marine and Anadromous Species|
Characterize vital rates and other demographic parameters for key species, and develop and improve methods for predicting risk and viability/sustainability from population dynamics and demographic information.