Salmon Steward

HOW COULD CLIMATE CHANGE AFFECT BRITISH COLUMBIA? The impacts of climate change are a lready aecting us in B.C. Sea levels are rising, and in the Fraser River, summer flows are declining while water temperatures are rising. Things are likely to get worse, with increased annual rainfall, earlier snowmelt and much less snow. All this extra rainfall means more flooding and storm conditions. Combined with warmer rivers, drier summers and sea-level rise, the challenges to salmon in freshwater will be substantial. In the ocean, average annual sea surface temperatures have increased up to 1.4 C since 1935, with even higher increases in summer temperatures. To put some of this into perspective, when temperatures rise above 22-24 C, adult salmon start to die. The Fraser Sockeye fishery was closed in 2016 when river temperatures reached 20.6 C. Other eects in the ocean will include: changes in currents and circulation; increased ocean acidification; reduced oxygen for marine creatures; increased frequency of harmful algal blooms; and rising sea levels, which could drown estuaries and nearshore habitats. HOW CAN CLIMATE CHANGE AFFECT SALMON? Some key impacts could include: • Increased storm intensity that can scour streambeds and kill salmon eggs. • Warmer water temperatures during egg incubation that could cause fry to emerge too early, leaving them vulnerable to predators and mismatched with environmental cues. • Higher water temperatures (which hold less oxygen) could stress salmon returning to their natal streams. Some notable instances of Fraser Sockeye dying before spawning have already occurred in British Columbia. • We may start seeing smaller salmon. For example, higher sea surface temperatures have been correlated with smaller Fraser River Sockeye over the past 42 years. • Loss of important forage fish which are prey for salmon. • More stresses that increase salmon's vulnerability to pathogens, harmful algae and predators. • Predation on salmon could increase as predators like Pacific hake and mackerel move north. ARE SOME SALMON SPECIES AT GREATER RISK? Coho, Sockeye and some populations of Chinook, which remain in fresh water for the first year of their life cycle, are more vulnerable to changes in freshwater temperatures. Pink and Chum will likely be less susceptible, as they emigrate to the ocean immediately after emerging as fry. However, those juvenile salmon that leave the rivers at a smaller size show a far greater reliance on estuaries and nearshore habitats: these salmon would be at risk if these habitats become submerged during sea level rise. The Fraser River drainage in British Columbia accounts for 30 to 40 per cent of all Pacific salmon produced in Canada. Because many Sockeye, Pink and Chum salmon stocks are at or near the southern limit of their range in the Fraser, where temperatures are warmer, the early impacts of climate change should be detectable in these stocks first. 22 2018 psf.ca Dr. Isobel Pearsall PROJECT COORDINATOR, SALISH SEA MARINE SURVIVAL PROJECT WHO CARES ABOUT SALMON? Probing the link between climate change and salmon survival Climate change resulted in rapid growth of the mountain pine beetle and the loss of millions of hectares of pine forest in British Columbia.

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