Fraser River sockeye salmon: data synthesis and cumulative impacts

sockeye stocks tended to coincide with periods of high productivity in western Alaskanstocks, and vice versa.The Cohen Commission is interested in factors affecting the Fraser sockeye fishery, not onlyFraser sockeye productivity. Over the last two decades there has been an increasing amount ofen-route mortality of returning Fraser sockeye spawners (i.e., mortality between the Missionenumeration site and the spawning ground), as illustrated for late run sockeye in Figure 4.1-5.This results in reduced harvest, as fishery managers do their best to ensure enough spawnersreturn to the spawning ground in spite of considerable mortality along the way. Since en-routemortality is already included in estimates of recruits, it does not affect estimates of productivity,but it does affect the fishery.Other patterns noted by McKinnell et al. (2011) have particular relevance to the low 2009 returns(2007 ocean entry for most sockeye), and provide some interesting contrasts among stocks withdifferent life history patterns and migratory pathways:o most Fraser River sockeye stocks had very poor returns/spawner in 2009, but;o Columbia River sockeye had double their average returns in 2009 (recruits/spawner notavailable),o hatchery-reared sockeye from Cultus Lake showed typical survival rates through theStrait of Georgia in 2007 (estimated from tracking acoustic tags), ando there were record high returns of Harrison River sockeye in 2010, from underyearlingsthat reared in the Strait of Georgia in 2007.32