As climate change warms the planet at unsustainable rates and causes lengthy droughts, species that thrive in colder waters, like salmon, face an onslaught of challenges. Between the high temperatures and the pathogens that thrive in them, endangered salmon on the West Coast of the United States are experiencing massive die-offs. This is already driving up the price of fillets, the Associated Press reports, and the ecological and economic effects of the losses will ripple into the future. The Sacramento River faces “near-complete loss” of young Chinook salmon because of the warming water.
“An extreme set of cascading climate events is pushing us into this crisis situation,” spokesperson Jordan Traverso of the California Department of Wildlife and Fish tells the AP.
Nowhere is the scope of the problem more visible than the Klamath river, an important route for salmon migration, which flows from Upper Klamath Lake in Oregon to California. The river is of special importance to the Yurok tribe, as their ancestral land on the California coast includes where the Klamath empties into the Pacific Ocean. The Yurok heavily depend on the river’s salmon for fishing and cultural reasons, so the tribe regularly monitors the animals for Ceratonova shasta, a lethal parasite of the fish. In a May statement, the tribe reported that in two tributaries of the Klamath, 97 percent of all juvenile salmon caught for monitoring were infected and 70 percent of the fish turning up in their live traps were already dead.
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The West’s salmon populations were already feeling the effects of climate change. Each spring, the fish swim upriver from the Pacific Ocean to lay their eggs in the cold waters that run off of melting mountaintop snowpacks. As warmer temperatures decrease the amount of snowpack that builds up each year, less water is available in the rivers, and some of what’s left is diverted for human use, further reducing water flow and the habitat available to the salmon. Also, the less water there is, the faster it heats up, creating circumstances too warm for salmon to breed, hunt for food, or even survive.
In addition, parasites such as C. shasta thrive in these conditions. Diverting water from reservoirs to rivers with exploding parasite populations may help flush them from the salmon’s breeding grounds, but with the region’s historic drought, water is at a premium. In May, for instance, the US Bureau of Reclamation opted not to divert more water to the Klamath, citing drought and limited resources.
Among the critics of that choice are members of the Yurok tribe. “We are watching a massive fish kill unfold in real-time,” Barry McCovey, Yurok Fisheries Department Director, says in the May statement from the tribe. “The juvenile fish kill will limit salmon production for many years to come. It will also negatively impact many other native species, ranging from orcas to osprey, because salmon play such an essential role in the overall ecosystem.”
Sam Mace, director of the salmon conservation organization Save Our Wild Salmon, tells the AP that these circumstances will only become more common across the Western US as the pressures of climate change continue. “We need some real changes in how rivers are managed if [wild salmon are] going to survive.”