Warming Northwest Rivers Raise Risk Of Fish Kills

Jun 29, 2015

It’s been a one-two punch of low snowpack last winter and not enough rain this spring for many Northwest rivers. Warm temperatures and low river flows are causing problems for salmon making the return migration.

In rivers and streams across the Northwest, waters are reaching a tipping point for salmon. Salmon like water temperatures to be 68 degrees. Officials say water temperatures in June are what is normally expected in late August.

Temperatures in the Willamette River rose five degrees in one week. The Portland Harbor area has seen about 200 fish die off — mostly chinook salmon but also a some sturgeon and steelhead.

Rick Swart, Oregon Department of Fish and Wildlife spokesman, said one silver lining is that there has been a large run of spring chinook this year.

“Certainly we expect conditions to become more pronounced farther into the summer. One of the concerns is resident fish. Migratory fish, the salmon, are going to die anyway, but when you start seeing sturgeon and steelhead and species that kind of stick around a little bit more, that’s more problematic,” Swart said.

On the Skagit River in northwestern Washington, temperatures are also high and flows are low. Scott Schuyler, policy representative for Upper Skagit Indian Tribe, said he has grave concerns for salmon runs.

“The effects will be long lasting,” Schuyler said of future salmon runs.

With some tributaries slowing to a trickle, Schuyler said he’s worried about offspring from last year being stranded without water. He’s also worried about what will happen when expected large numbers of pink and coho salmon return in August and September with nowhere to go.

“I just don’t know what’s going to happen to them,” Schuyler said. “I don’t expect to have any water for them. It affects the spawning, it affects their behavior, and it’s going to affect their future returns.”

Hatchery managers have had to release fish early throughout the Northwest.

On Oregon’s Sandy River, the ODFW is now allowing anglers to fish from float tubes, drift boats, and kayaks so that they can reach fish.

Water temperatures are also warming on the mainstems of the Columbia and Snake rivers, but managers there haven’t yet seen as many problems as some of the tributaries.

On the mainstem Snake River fish managers are able to release cool water from the Dworshak Reservoir, which helps control temperatures for fish. Paul Wagner, biologist with NOAA Fisheries, said right now temperatures are at a record in the Snake River Basin.

“This year we started early, and we’re ramping up fast,” Wagner said. “It’s disturbing that temperatures are so warm so quickly and that flows are so low so quickly. It’s far from ideal.”

The ODFW has issued guidelines calling for people who happen to come upon a salmon carcass along river banks to either leave it alone or gently roll it into the river. They said to keep dogs away from salmon because salmon can be poisonous to dogs.

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