Invasive Chinese Mitten Crab Confirmed in Willamette River
ODFW urges public to help identify and report the prohibited species after a second sighting in Oregon
SALEM, Ore. — The Oregon Department of Fish and Wildlife (ODFW) has confirmed the discovery of a Chinese mitten crab in the Willamette River near Portland, marking the second verified sighting of the invasive species in Oregon this year.
The crab was reported on Nov. 17 after it was spotted in shallow water near the Sellwood Bridge and captured by hand. It was alive at the time it was found and was not released back into the river.
The Chinese mitten crab, a prohibited species in Oregon, lives its adult life in freshwater but migrates to brackish water to breed—unlike Oregon’s native crab species, which inhabit marine environments such as bays, estuaries, and the ocean.
According to ODFW, the sighting follows a separate confirmed detection earlier in April 2025, raising concerns about whether additional mitten crabs may be present in Oregon waters.
Image: ODFW
ODFW biologists are 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 assess the situation. Monitoring efforts include shoreline surveys, collecting water and substrate samples for mitten-crab-specific genetic markers, and deploying artificial habitats designed to attract the species. PSU researchers have also initiated shoreline walks along the Columbia and Willamette rivers to search for signs such as molted carapaces.
Mitten crabs are illegal to possess or sell in Oregon. The agency warns that unlawful imports for the food trade—where the species is sometimes sold live—pose a risk of accidental or intentional release into Oregon waterways. ODFW encourages the public to report any suspected illegal sales.
Residents who encounter a crab they believe may be a Chinese mitten crab are asked to report it by calling 1-866-INVADER or by submitting a report through the Oregon Invasive Species online hotline. Photos can be uploaded to assist biologists with identification, as native species are sometimes mistaken for mitten crabs.
The invasive crab can cause significant environmental damage by burrowing into dikes, levees, and streambanks, increasing erosion and threatening flood-control and water-supply systems. The species also preys on native aquatic life, consumes fish eggs, and competes for food, potentially impacting native fish and crayfish populations.
Chinese mitten crabs are medium-sized, roughly three inches across, and range in color from brownish orange to greenish brown. They are named for the dense, hairy patches on the outside of their claws. Key identification features include a notch between the eyes and four spines on each side of the carapace.
ODFW notes that Oregon’s native hairy shore crab also has patches of hair on the inside of its claws, underscoring the importance of submitting photographs for proper identification.
ODFW has provided a visual guide for crab identification and cautions the public not to harm native species.
Cover image: ODFW
