Fraser River sockeye salmon: data synthesis and cumulative impacts

changes in Fraser sockeye stock productivity. As discussed in section 4.7, these effects are mostlikely to occur in Stage 4 (growth in the North Pacific and return to the Fraser).McKinnell et al. (2011) investigate how marine conditions along the coast may potentially haveaffected Fraser River sockeye salmon over recent decades and the 2005 brood year (2009returns) in particular. The physical conditions examined include wind, river discharge, salinity,temperature, water density, and water column stability. The primary biological conditionsexamined were the timing and magnitude of chlorophyll production. Broad scale climate driverscan influence river discharge and wind regimes, which may then influence the salinity of coastalwaters. Salinity and temperature interact to affect water density, water column stability andtherefore surface mixing, which impacts the productivity of the surface layer and its potential toincrease in temperature. Fraser sockeye salmon are negatively affected by warmer and lessproductive ocean conditions. McKinnell et al. (2011, Sections 6.1, 6.2) explore the oceanographyand climate of the Strait of Georgia and Queen Charlotte Strait/Sound.Johannes et al. (2011) explore how human activity and development in the areas surroundingStrait of Georgia may potentially have had a negative impact on habitat quality for sockeyesalmon as they leave the Fraser River estuary. Changes in the human population may be a proxyfor many feasible mechanisms by which human activity and development might directly impactsockeye salmon habitat quality. Increasing contaminants in the Strait of Georgia from mills,industrial facilities, chemical inputs to farming, and liquid and solid waste inputs couldpotentially degrade habitat quality. Forestry is a major land use in the areas surrounding theStrait of Georgia. Although forestry has been shown to often have a negative effect on freshwaterand estuary habitats for salmon, the potential impact on inshore marine habitat is uncertain(Johannes et al., 2011). Increased marine traffic may also create transient disturbances upon thesurface and contribute further contaminants to the water.Climate change could potentially have driven broad scale changes to the entire ecosystem(Hinch and Martins, 2011). It is plausible that climate change may have contributed to changesin the timing, magnitude, patterns, trends and variability in physical and biological habitatconditions along the coast. The potential impacts to sockeye salmon could be direct, such asincreases in sea surface temperature, or indirect, such as changes in predation, disease, or foodabundance and quality.4.4.2 Exposure of Fraser River sockeye to stressorsMost of the evidence on exposure to particular stressors during this life stage is based on anunderstanding of the general migration route and timing of Fraser River sockeye salmon and an58