Oregon’s North Coast is experiencing a mass die-off of fall Chinook salmon due to abnormally dry weather, prompting the Oregon Department of Fish and Wildlife (ODFW) to shut down all salmon angling through December 31.
The die-off was first observed in the Wilson River near Tillamook, where ODFW found at least 200 adult salmon dead. Further investigation revealed similar rates of mortality in the Nestucca, Trask and Kilchis rivers.
According to Robert Bradley, district fish biologist for ODFW’s North Coast Watershed District, during their migration the salmon became trapped in small pools of water due to the lack of precipitation. There they were vulnerable to leeches carrying a parasite called cryptobia.
ODFW was quick to assure that cryptobia is not dangerous to humans, as it only affects certain breeds of fish. However, it has proved unusually lethal to fall Chinook this year.
“This scale of die-off is really unheard of,” Bradley told the Statesman Journal. “This parasite typically doesn’t escalate to this level.
“Luckily we did have rain in October, so some fish were able to move upstream and spawn before it dried out. Long-term it will depend on how many more fish come in — which usually lasts until January — and can get eggs in the gravel. That’s why it’s so important to protect what’s left.”