Idaho Statesman Tanushri Sundar (TNS)
BOISE, Idaho — In less than 20 years, wild chinook salmon could be extinct. But a group nestled in the rugged wilderness of central Idaho could be the key to the recovery of the endangered species throughout the northwest.
Protecting salmon in the middle fork of the Salmon River will be especially critical to the survival of the species, several scientists told the Idaho Statesman. Chinook salmon born in the pristine waters of the Middle Fork may be able to adapt to climate change, researchers say, and if larger threats such as hydroelectric systems are removed, wild salmon may have a chance to survive. to beat.
The Middle Fork is the “crown jewel” of salmon habitat in the northwest, said Idaho Fish and Game fisheries biologist Tim Copeland.
“These are the best populations,” Copeland said. “And if they can’t make it, none of them will.”
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A critical habitat
Spanning 2,800 square miles of nearly untouched wilderness, Middle Fork is home to nearly every species that was there when Lewis and Clark arrived in the early 1800s. most productive in the Pacific Northwest.
Almost all Middle Fork Chinooks are feral, which means they have not bred with hatchery-bred salmon. Wild fish have great genetic diversity — a rarity in the Columbia River Basin, said Scott Brandt, fisheries biologist at Boise National Forest.
Genetic diversity is key to resilience and therefore key to species survival, Brandt said. With the highest number of salmon returns per spawning adult reported in the scientific literature, the Chinooks of central Idaho quickly take advantage of favorable conditions.
The salmon also spawn at 6,000 feet, the highest elevations of any spring and summer chinook salmon population in the world, Brandt said. The frigid waters contribute to a vast and vibrant landscape, with plenty of habitats to support salmon throughout their life cycle, he added.
Even so, the Middle Fork Chinook is in precipitous decline, with low abundance and low productivity over the past five years, said Russ Thurow, a fisheries research scientist at the Rocky Mountain Research Station. Scientists estimate that Chinook populations in the region are 3% of what they were in the 1950s and 1960s, and that even those populations could have been around 30% of what they were in the 1870s.
For two million years, chinook salmon inhabited the Salmon River, Thurow said, and they evolved alongside fires, storms and debris flows. Thurow expects the Middle Fork Chinook to be best positioned to adapt to future challenges such as climate change.
Reduced stream flow, rising water temperatures and unprecedented wildfires are major climate impacts on Idaho salmon, said Rocky Mountain Research geomorphologist John Buffington. Station. Another concern is variability in stream flows, causing periodic droughts or floods that destroy fish nests, Buffington added.
“In order to deal with what’s coming with climate change, we really need those kinds of populations,” Thurow said.
As other salmon at lower elevations and with less adaptability wade through warmer temperatures due to climate change, scientists may one day use the Middle Fork Chinook to replenish fishing grounds in lower elevation habitats, a said Thurow. This would require national and international climate change mitigation efforts, Thurow added, so that the fish are not overtaken by their changing environment.
And the Middle Fork is best suited to sustain future populations, Thurow said, because it can support many more fish than currently live there.
Threatened by dams
However, the cool waters of the salmon river do not help Middle Fork chinook when they migrate. Middle Fork chinook remain threatened by out-of-basin challenges away from their spawning grounds, and their numbers may continue to decline even as they adapt to climate change.
“That’s where the main bottleneck is,” Thurow said.
Fisheries biologists use the “four Hs” — habitat, hatcheries, harvest and hydropower — to define salmon recovery. In the Middle Fork, fish are safe from three of those impacts — their habitat is intact, they’re free of hatcheries, and their harvest is low, Thurow said. The only impact comes from hydroelectricity.
Middle Fork Chinook encounters deadly obstacles on its journey to the ocean as a young salmon, then returns to its spawning grounds as an adult, Thurow said. Studies suggest that dams and reservoirs hurt salmon numbers the most because they make it harder for live fish to pass through.
The dams don’t allow for a free-flowing river, said Kurt Tardy, anadromous fisheries biologist for the Shoshone-Bannock Tribes. The dams hold back water, create reservoirs and slow the salmon’s travel times, Tardy said, which exposes the fish to dangers such as heat or predators.
The federal government has spent more than $17 billion on wild fish mitigation strategies that haven’t increased fish numbers, said U.S. Rep. Mike Simpson, R-Idaho, who proposed last year to break four dams on the lower Snake River in Washington. Last month, the White House released two reports indicating that removing these dams may be necessary to restore salmon runs at an estimated cost of between $11 billion and $19 billion.
The extinct chinook salmon would be an ecological and recreational loss, especially for Idahoans who depend on these fish, Thurow said.
“It would be an almost inconceivable loss for us,” he said.