A potentially damaging invasive freshwater crab species was captured in an Oregon river in mid-November, raising concern for the Oregon Department of Fish & Wildlife (ODFW). The Chinese mitten crab can cause erosion, compromise flood control, and threaten native crab populations.
This marks the second mitten crab reported in an Oregon river in 2025, following the first sighting in April. The latest crab was found alive in shallow water in the Willamette River near Portland on November 17. It was caught by hand and was not returned to the river.
Unlike Oregon’s native crabs, which live in oceans, bays, and estuaries, Chinese mitten crabs spend their adult lives in freshwater and reproduce in brackish waters, ODFW said.
The species is named for the hair-like “mittens” on its claws. They also have a notch between their eyes and four spines along the sides of their bodies. Medium-sized, about three inches wide, mitten crabs can range in color from brownish orange to greenish brown.
These crabs burrow into stream banks, levees, and rock walls, which can accelerate erosion and damage flood control and water supply systems. They also prey on native species, eat fish eggs, and compete for food, potentially affecting local fish and crayfish populations.
Possession and sale of mitten crabs is illegal in Oregon. ODFW urges anyone who spots a crab resembling a Chinese mitten crab to report it by calling 1-866-INVADER or using the online Oregon Invasive Species reporting hotline.
The agency is working with the U.S. Fish and Wildlife Service, Portland State University’s Center for Lakes and Reservoirs, and the Oregon Invasive Species Council to determine whether additional mitten crabs are present in the Willamette River.