ASTORIA, Ore. (AP) — Fishing for fall chinook is now banned in multiple rivers on Oregon’s north coast because extremely dry conditions have fueled a widespread die-off of the species.

After two months of low rainfall, hundreds of adult fish on multiple coastal streams are dying from an unusual outbreak of a naturally occurring parasite before they get a chance to spawn, according to Oregon Public Broadcasting.

Extended periods of low water levels mean that salmon waiting to swim upstream to spawn are spending extra time in shallow water where conditions are more conducive to the cryptobia parasite, the Oregon Department of Fish and Wildlife said.

The parasite doesn’t pose a risk to humans and only affects certain species of fish.

ODFW tells the station that it found at least 200 dead fish when it searched the Wilson River near Tillamook after getting reports from the public of scores of dead fish. That river closed to fishing earlier this month and ODFW found similar die-offs on the Nehalem, Trask and Kilshis rivers.

That prompted an additional ban on fall chinook fishing on the Nestucca to Necanicum rivers, as well as bays.

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Steelhead fishing season is not affected.

Robert Bradley, a district biologist for ODFW, said the parasite has killed far more fish this year than it ever has before, and it’s cutting down an already depleted run of fall chinook.

“We need to protect the remaining spawners to help provide for future runs of fall chinook on the North Coast,” he said.

National Weather Service hydrologist Andy Bryant says some river flows on the north coast have dropped to just 10% of normal in the past two months.

“Normally for the north Oregon Coast Range we’d be seeing quite a bit of rain and we just haven’t seen that,” Bryant said. “So the river has pretty much just stayed at the low flows we had seen earlier in the fall. With the lack of rainfall it hasn’t started to come up like it typically would.”

Bryant said conditions are abnormally dry across most of the Oregon and the Pacific Northwest.