Fraser River sockeye salmon: data synthesis and cumulative impacts

Peterman and Dorner (2011) analyzed data sets on the abundance of spawners and their resultingreturns for a total of 64 populations ("stocks") of sockeye salmon, including 19 from the FraserRiver, and the rest from other parts of British Columbia, Washington state, and Alaska (Figure4.1-2). Only 4 of these 64 stocks were substantially affected by other potentially confoundingfactors (Pitt, Cultus – hatcheries; Great Central Lake and Sproat - lake fertilization) so the overallproductivity patterns are representative of natural wild sockeye populations. Peterman andDorner also obtained data on juvenile abundance in fresh water for 24 of these and other sockeyepopulations to determine if problems were mainly in fresh water or the ocean. They used threemeasures of productivity: 1) the number of returning adults (recruits) per spawner 7 , whichincludes the effects of spawner abundance on productivity; 2) annual residuals in productivity,which describes how productivity diverged from what would have been expected each year justbased on spawner abundance; and 3) Kalman filter estimates of long term trends in productivity,which extract productivity trends from year-to-year noise.AlaskaYukon41-4263 43386439-40 3731-3255-624833-36 3053-5444-47,2951-522849,5026-272523-24B.C.Fraser River (2-20)21-221Figure 4.1-2. Locations of ocean entry for seaward-migrating juveniles of the 64 sockeye salmon populations withtime series data on annual abundances of spawners and the resulting adult returns or recruits. Source:Peterman and Dorner (2011).7 Recruits are estimates of the abundance of returning spawners in coastal fishing areas prior to harvest and post-Mission en-route mortality, estimated for each stock as: [ (estimated adults on the spawning ground) + (estimatedmarine and freshwater harvest) + (estimated post-Mission en-route mortality) ].30