Fraser River sockeye salmon: data synthesis and cumulative impacts

salinity. There is much evidence that very warm years tend to negatively affect certaincharacteristics of Fraser River sockeye salmon biology (McKinnell et al., 2001, Section 3.5).This broad scale shift in oceanographic conditions coincides with a “shift” in median FraserRiver sockeye salmon productivity that may have also occurred in 1992. McKinnell et al. (2011)propose that the underlying pattern of a marked shift in productivity occurring in 1992 provides abetter fit to the observed productivity data than does the idea of a gradual decline over time andthat there are other comparable sockeye stocks on the west coast that exhibited similar declinesbeginning in 1992, though many of those stocks subsequently demonstrated recovery with the1998/99 la Niña. In 2007, the Gulf of Alaska was generally cool, which is not consistent with thepoor returns observed in 2009. In terms of biological ocean conditions, McKinnell et al. (2011)state that for the open ocean, “there is no trend in average nutrient concentrations in the southernGulf of Alaska (Station Papa) since the 1950s, no trend in average chlorophyll a since 1998, andno trend in average zooplankton biomass.Hinch and Martins (2011) report that it is possible that the survival of immature sockeye salmonhas decreased in association with climate change. Although there are no lab data and little fielddata on the response of adult sockeye to climate change in the open ocean, it does appear thatFraser River sockeye salmon survival is negatively correlated to the sea surface temperature oftheir last few months at sea (Hinch and Martins, 2011, Section 1.4). They further report that seasurface temperatures in the Strait of Georgia and the Gulf of Alaska have been consistentlyincreasing since the 1950s, while sea surface salinity and pH have been decreasing over the sameperiod (Hinch and Martins, 2011, Section 1.5). However, there is also evidence that much of theobserved warming trend can be attributed to the 1977-1997 positive phase of the PDO, ratherthan longer-term changes in climate (Hinch and Martins, 2011, Section 1.5).Returning Fraser River sockeye salmon will encounter the same potential stressors associatedwith human activity and development surrounding the Strait of Georgia as described in Section4.4, though the extent of this exposure will vary based on the rate of northern diversion, asdescribed above in Section 4.5.2.4.5.4 Correlation/consistency with patterns in non-Fraser River sockeyeproductivityOur comments here are identical to those for Stage 3 in section 4.5.3. Many other sockeye stocksshare the same habitat of the North Pacific Ocean with Fraser River sockeye salmon. Stocks thatshare both geographic and temporal overlap in the open ocean will likely encounter similarpathogens, predators and ocean conditions during this stage. The extent to which such stocksshow similar trends in productivity to those of the Fraser River (see Peterman and Dorner, 2011)77