What, here come Coho?

LEABURG: Why Coho salmon have decided to make a showing locally is a question that remains unanswered. Starting last October 4th, over 50 have been spotted in the waters of the McKenzie River. And, they’re making a showing in other areas, with a record-breaking 40,000 observed passing upstream at Willamette Falls. That number was the largest since record-keeping began in 1951.

Oregon Dept. of Fish & Wildlife biologist Jeff Ziller said they first had an inkling something out of the ordinary was occurring when a few fish appeared to be “just going crazy and were hard to net” in the trap at the left bank of the Leaburg Dam last fall. On closer inspection, they had the distinctive white gums and spotting that ID’ed them as Coho.

“That was news to us,” Ziller said. “We count fish every year and only saw one before at the Leaburg Hatcher fish trap two years ago, but not at the fish ladder.”

Their appearance, though, is not an indicator they’re returning to streams where they had initially spawned. Instead, they’re likely among the 5% of the Coho population who have set out as “pioneers.” They’re part of an overall 20-year trend that has seen expansions in the Willamette River and its tributaries. 40,000 Coho came over Willamette Falls last year, 15,000 greater than the number of Chinook that were tabulated.

The last major hatchery coho releases occurred in the upper Willamette basin in the late 1980s. Since then, ODFW’s hatchery practices have changed as fishery managers worked on rebuilding listed spring Chinook and steelhead populations.

McKenzie River District Fish Biologist Jeff Ziller describes the coho situation as a “new wrinkle” for fish managers.

“We don’t know whether coho are going to be a regular occurrence or what potential impacts to threatened upper Willamette Spring Chinook might be,” he said. “In the McKenzie, there has been ongoing, extensive restoration focused on increasing spawning and rearing habitat for spring Chinook above Leaburg Dam and we would like to know how coho might interact with those efforts.”

For now, the numbers aren’t a significant management concern but fish biologists are taking note.

Ziller is considering radio tagging a sub-sample of coho at Leaburg Dam next year to determine where they’re spawning to assist in assessing potential impacts. ODFW is also looking at changing angling regulations to allow the harvest of coho in the McKenzie River below Leaburg Dam, though that fishing opportunity is expected to remain minimal.