The five species of Pacific Salmon found along the west coast of North America are anadromous – they migrate from the ocean to freshwater to spawn. Each stock is genetically adapted to the environment in which it resides and exhibits unique characteristics such as migration route, migration timing, and productivity.
NOAA Fisheries published a new report on July 24, 2019, in PLOS ONE. The report, the second in a series of planned NOAA Fisheries’ vulnerability assessments, gauges the vulnerability of Pacific salmon by analyzing 33 threatened or endangered groups, including local populations from the Mexican border to the Canadian border.
Researchers have identified four Pacific salmon populations in California, Oregon, and Idaho that are particularly vulnerable to climate change. All of these populations are on the federal endangered species list.
They include the Chinook salmon in California’s Central Valley and in the Columbia and Willamette River basins in Oregon; coho salmon in parts of Northern California and Oregon; and sockeye salmon that reach the Snake River Basin in Idaho.
Lisa Crozier, a salmon researcher, and lead author of the study explained that these populations were found to be bumping into temperature limits, and those that spawn far inland after lengthy summer stream migrations and those that spend a lot of time in coastal habitats like river estuaries are among the most at risk.
These populations will have to survive in warmer water, more acidic ocean conditions and even seasonal streamflow conditions caused by global warming and other human impacts, Crozier added. “They are very resilient and opportunistic. That’s why we have hope. We just have to give them half a chance,” she said, according to Inside Climate News.
Crozier says salmon populations since the building of dams have managed to survive by adapting to some warming and reduced streamflow, however, she also says that if global warming goes beyond 2 degrees Celsius (3.6 degrees Fahrenheit) of warming compared to pre-industrial times, “all bets are off.”
Climate crisis hits salmon with a one-two punch
The study spells out several ways that global warming is endangering salmon populations:
* Young salmon will die when water temperatures warm above a certain threshold. This very thing happened in August 2018 on British Columbia’s Fraser River. Not only was the river’s temperature too high for salmon – they do well when the temperature is below 17 degrees Celsius (62.6 degrees Fahrenheit) – but streamflow was also down.
* Flooding can also flush eggs and young fish from their nests. Add to this the risks from silt-filled rivers running high or out of their banks and this spells disaster for salmon, especially in California with its extreme atmospheric rain storms.
* Warmer temperatures are also increasing the risk of fish diseases in a salmon population already made vulnerable because of global warming. From “white spot disease,” caused by a microscopic parasite called Ichthyophonus hoferi, to the Japanese broad tapeworm, Diphyllobothrium nihonkaiense, and sea lice, salmon are being hit with a one-two punch.
