A commercial fisherman working the Lower Columbia River near Tongue Point landed more than he bargained for last week, snagging Oregon’s first confirmed Chinese mitten crab.
The Oregon Department of Fish and Wildlife (ODFW) reported that the large male specimen was caught on April 22 and immediately brought to agency staff on the Columbia. From there, ODFW shellfish biologists identified the crab as Eriocheir sinensis, a prohibited invasive species notorious for wreaking havoc in other U.S. waterways.
Chinese mitten crabs are named for their dense, hairy claws and can be distinguished by a notch between the eyes and four spines along either side of their carapace. Coloration ranges from brownish orange to greenish brown. Native crab species can sometimes be misidentified, so ODFW urges river users to pay close attention and report anything that matches the mitten crab’s description.
“While this is a rare event in Oregon, mitten crabs caused significant infrastructure and ecological damage in and around San Francisco Bay when the population was at its height in the late 1990s,” the agency warned in a news release. The invaders burrow into banks and levees, increasing erosion, and can outcompete native species.
According to Oregon Live, this is the first confirmed sighting of a Chinese mitten crab in the Pacific Northwest. A single Japanese mitten crab was discovered in the same general area back in 1997, but the Chinese species had never been officially recorded in these waters until now.
Mitten crabs spend most of their lives in freshwater but must migrate to saltwater to reproduce. Their life cycle, combined with the possibility of larvae being introduced via ballast water or intentional release, makes them particularly challenging to control.
ODFW is now working in partnership with the Washington Department of Fish and Wildlife and NOAA to determine whether more mitten crabs are present in the Columbia River system. Biologists are deploying trap lines and may use environmental DNA sampling to track species’ presence.
In the meantime, commercial and recreational river users are being called on to act as the first line of defense. Anyone who spots a mitten crab is urged to take a photo, note the location, and report it to their local DFW office.
