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How long before these salmon are gone? ‘Maybe 20 years’

NORTH FORK (Idaho) — The Middle Fork of the Salmon River, one of the wildest rivers in the contiguous United States, is prime fish habitat. Cold, clear waters from melting snow tumble out of the Salmon River Mountains and into the boulder-strewn river, which is federally protected.

How long before these salmon are gone? ‘Maybe 20 years’

NORTH FORK (Idaho) — The Middle Fork of the Salmon River, one of the wildest rivers in the contiguous United States, is prime fish habitat. Cold, clear waters from melting snow tumble out of the Salmon River Mountains and into the boulder-strewn river, which is federally protected.

The last of the spawning spring-summer Chinook salmon arrived here in June after a herculean 800-mile upstream swim. Now the big fish — which can weigh up to 30 pounds — are finishing their courtship rituals. Next year there will be a new generation of Chinook.

Despite this pristine 112-mile-long mountain refuge, the fish that have returned here to reproduce and then die for countless generations are in deep trouble.

Some 45,000 to 50,000 spring-summer Chinook spawned here in the 1950s. These days, the average is about 1,500 fish, and declining. And not just here: Native fish are in free-fall throughout the Columbia River basin, a situation so dire that many groups are urging the removal of four large dams to keep the fish from being lost.

“The Columbia River was once the most productive wild Chinook habitat in the world,” said Dr Russ Thurow, a fisheries research scientist with the Forest Service’s Rocky Mountain Research Station.

Standing alongside the Salmon River in Idaho, Dr Thurow considered the prospect that the fish he had spent most of his life studying could disappear. “It’s hard to say, but now these fish have maybe four generations left before they are gone,” he said. “Maybe 20 years.”

Thirteen species of salmon and steelhead trout are listed as threatened or endangered in the Columbia basin, an area that includes parts of Idaho, Oregon, Washington, Montana and British Columbia. Salmon are a keystone species in this region, critical as a food source for animals such as bears, eagles and insects.

That group of beneficiaries includes an endangered population of orcas, or killer whales, along the West Coast that survive by eating Chinook in the winter and spring, up to 30 a day.

WARMING WATERS

Chinook, or king salmon, are huge, powerful fish, the largest member of the salmon family in North America. Spring-summer Chinook make an epic migration thousands of miles through the Columbia River to the waters surrounding Alaska’s Aleutian Islands, and then back to the high elevations of the Rocky Mountains.

Before the 20th century, some 10 million to 16 million adult salmon and steelhead trout are thought to have returned annually to the Columbia River system. The current return of wild fish is 2 per cent of that, by some estimates.

While farming, logging and especially the commercial harvest of salmon in the early 20th century all took a toll, the single greatest impact on wild fish comes from eight large dams — four on the Columbia and four on the Snake River, a major tributary.

The four Snake River dams are used primarily to create reservoirs for the barging of Idaho’s wheat to ports. But the dams raise water temperatures and block travel migration routes, increasing fish mortality.

Climate change also has raised both river and ocean water temperatures, which can be deadly to fish. In 2015, for example, unusually warm water killed an estimated 250,000 sockeye salmon.

For decades, experts have tried to ameliorate the loss of the Columbia’s wild fish by installing ladders that allow the fish to swim around the dams, and by placing them in barges and trucks for transport around the dams. The massive efforts have not stemmed the decline, despite the fact that more than US$16 billion has been spent on recovery over the last several decades.

Now most scientists come down on the side of removing the dams. Last fall, orca researchers urged Governor Jay Inslee of Washington and the Southern Resident Orca Task Force, a state government panel, to begin removing the four dams on the Snake River to aid the starving whales.

“Put simply, orca need more Chinook salmon available on a year-round basis, as quickly as possible,” they wrote, calling the removals “vital to ensure orca survival.”

The federal agencies responsible for managing fisheries on the Columbia, though, maintain that removing the Snake River dams is not critical to the survival of salmon and that hatchery-reared fish have made up for the loss of the river’s wild fish for the orcas.

The southern resident killer whales “do not distinguish between hatchery and wild fish,” the Northwest Fisheries Science Centre, part of the National Oceanic and Atmospheric Administration, said in a statement.

The National Marine Fisheries Service has proposed killing more than 1,100 sea lions along the Columbia River because they eat salmon as they gather to spawn.

Those who want to keep the dams point to changing ocean conditions as a major factor in the decline of the salmon. Water temperatures have been unusually warm in recent years, which reduces salmon food sources. Federal officials just announced that the marine heat wave has returned this year.

But hatchery fish are not the same, said Dr Deborah A. Giles, science and research director at Wild Orca, a group that studies and advocates for protection of the whales. Orcas evolved eating big wild fish, some 300 to 350 pounds a day.

“Wild fish are much bigger and more lipid-rich,” she said. “Having to catch the equivalent of 350 pounds in hatchery fish, which are smaller and lower quality, expends significantly more energy. They have to work a lot harder for their meals.”

A GRUELING JOURNEY

The extreme migration of the spring-summer Chinook salmon is one of the natural world’s great journeys.

Before the dams were built in the 1960s and 1970s, the fish born in the Middle Fork were swept by strong spring currents 800 miles to the sea. The rivers moved them rapidly along, from 6 to 10 mph, and the young fish reached the brackish waters of the Columbia River estuary in a couple of weeks.

As they travel, the parrs, or young freshwater salmon, undergo a profound transformation called smoltification, becoming smolts able to thrive in saltwater. After leaving the river, the fish turn north and travel to the North Pacific, near the Aleutian Islands.

They spend up to four years feeding at sea, and then those that survive the seagoing journey return to the mouth of the Columbia. Their physiological changes are reversed as they move upstream, and they again become freshwater fish.

Picking up the scent of their natal stream, they fight the current, foregoing food on the grueling trip, gaining about 6,500 feet in elevation, and overcoming physical barriers in what biologists describe as a heroic journey.

“I’ve seen them jump an 8-foot waterfall, and they are known to jump 12 feet,” said Dr Thurow. “They are the definition of persistence.”

Chinook are known as “high-fidelity” spawners, not only returning to the stream where they were born, but also often to the same shallows. Then the game is afoot: In their waning days, as males battle for dominance, females excavate a redd, a depression in the gravel riverbed.

The female releases clusters of eggs as the male sidles up, releasing its sperm at the same time. The current mixes them, resulting in fertilisation. The eggs are adhesive and stick to the gravel after they fall. The female buries them in an egg pocket.

The mating is repeated multiple times; all told, some 5,000 eggs may be released by a single female. “By the time she finishes, she’s within a day or two of dying,” Dr Thurow said. The next spring, the offspring emerge and make their own journey to the sea. Always a gantlet, the migration now is far more deadly.

The eight large dams along the Snake and Columbia rivers created 325 miles of slack water in reservoirs. The average speed of the water flowing downstream has dropped to less than 1.5 mph, and it takes the fish far longer to reach the sea.

The Middle Fork of the Salmon River will be critical as the waters of the Columbia warm, Dr Thurow said. High-altitude streams are expected to warm less, and the Chinook here will find a cold-water refuge — and if they adapt, a base for repopulating other streams.

“The outlook isn’t good, but these fish are what give me hope,” Dr Thurow said. “Despite all of the obstacles, they are still here.” THE NEW YORK TIMES  

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