Wanted: Single Chinook Salmon For Spawning Fish Returning To Central Idaho Are Having Trouble Finding Mates, Biologists Say

Biologists scour central Idaho’s rivers for signs of spawning chinook salmon are seeing increasing evidence that returning fish are having trouble finding mates.

“We’re getting reports of these single fish swimming up and down the river,” said Mike Larkin, fisheries biologist for the Idaho Department of Fish and Game. “I guess there’s a very real possibility that those single fish are traveling extensively up and down the spawning grounds looking for a mate.”

Initial redd counts are grim on the Salmon River and its tributaries. A recent flight over tributaries revealed no redds in Valley Creek or the Salmon River above Sawtooth Hatchery near Stanley. Last year, the same stretches held nine and 10 redds respectively, Larkin said.

The same flight found five redds in the Lemhi, down from seven last year.

At the end of their 900-mile migration from the Pacific Ocean to the central Idaho spawning grounds, the female makes a redd in the riverbed to deposit the 5,000 or so eggs she carries and then waits for a male.

Once fertilized, the eggs are covered. In the spring, tiny sac fry will hatch and wiggle their way through the gravel. Only a small percentage of them will be strong enough to push their way through, and then only about 10 percent of them will live to become year-old smolts that migrate downstream.

Before eight hydroelectric dams blocked the Columbia and Snake Rivers, the females did not have a long wait. Tributaries to the Salmon River were teeming with chinook.

But this year, returning fish are few and females could well wait in vain until their biological clock ticks out. Once they leave the ocean, the fish stop eating. They are programmed to spawn, then die a few days later.

“When you get to these levels you start panicking, wondering, ‘Is there a male for these fish?”’ Larkin said.

There are a number of young males, less than a foot long, that for some reason have refused to migrate to the ocean with the other smolts. Typically, they are crowded out by the big returning adults.

“But now precocious males may well be important in preserving these last generations of chinook,” Larkin said. “They may be a natural safety mechanism.”