Chinese mitten crab.
Chinese mitten crab claws.
Chinese mitten crabs get their name from brown hairy patches on their claws resembling mittens. They spend the majority of their life in freshwater but reproduce in saltwater. Native to China and South Korea, they were first detected in the United States in the San Francisco Bay in the 1990s.
While these invasive crabs can arrive as larvae in the ballast water of cargo ships and be unintentionally released into new areas, Chinese mitten crabs have been intentionally smuggled into the U.S. and illegally introduced in the past.
In April 2025, Chinese mitten crabs were first detected in the Lower Columbia River in Oregon. They are not known to be in Washington.
Refer to WDFW's Crabs of Washington one-pager (PDF) for tips on identifying native and invasive crab species.
Invasive species information
Chinese mitten crabs prey on native species including clams, mussels, and fish eggs. They compete with native species for food and have been known to steal bait off angler's hooks and from fishing traps, damaging them in the process.
As a burrowing crab, they can damage riverbanks and levees, increasing erosion and leading to collapse of both natural and artificial structures. This in turn can lead to clogging of fish screens and pipes, hampering water delivery.
It is also a host to the Oriental lung fluke, Paragonimus westerman, which can infect humans when eaten raw or undercooked.
Description and Range
Physical description
Mitten crabs are light brown to green in color, with white tipped claws. The carapace width (distance across the back) of mitten crabs can reach 3 inches. The claws are approximately 1 inch wide.
Mitten crabs get their name from patches of hair on their claws said to resemble mittens. Juveniles may not have hairy claws, especially if smaller than 3/4 of an inch across. They have a notch between the eyes, four spines on each side of their carapace, a round body shape, and legs over twice as long as their body’s width.
Review WDFW's Crabs of Washington identification one-pager (PDF) for more information.
Ecology and life history
Adults live in freshwater rivers, estuaries, and brackish water but return to saltwater estuaries to reproduce. They construct burrows in river banks, levees, intertidal areas, and marsh bottoms. Juveniles consume mostly plants but adults prey mostly on animals like worms and clams.
Geographic range
Native to China and South Korea, they are found in coastal rivers and estuaries that drain into the Yellow Sea. They were first discovered in the United States in the San Francisco Bay estuary in 1992. In April 2025, they were discovered in the Lower Columbia River in Oregon.
They are not known to be in Washington though survey efforts by WDFW are ongoing.
Regulations
Rules and seasons
Chinese mitten crabs are not known to be found in Washington. If you suspect you have spotted one, please take a photo, note the location, and report your sighting online so WDFW can respond quickly. To protect native crabs which could be misidentified as Chinese mitten crabs, please leave the crab where you found it.
Chinese mitten crabs are classified as a Prohibited Level 1 Invasive Species in Washington, meaning live crabs may not be possessed or retained, introduced on or into a water body or property, or trafficked (transported, bought or sold), without department authorization, a permit, or as otherwise provided by rule. They are listed federally as injurious wildlife.
Under Washington state regulations, prohibited invasive species may be killed and returned to the water where they were found, or retained once dead, if the person is certain about species identification and assumes responsibility for correct identification and adherence to state rules and fishing regulations.
Considered a delicacy in parts of Asia, Chinese mitten crabs are edible but serve as a host to the Oriental lung fluke, Paragonimus westerman. Consuming raw or undercooked crabs can lead to infection in humans.