Chinese mitten crab (Eriocheir sinensis)

They’re not here—yet.

But if Chinese mitten crabs make their way into Puget Sound , they could pose a serious threat to freshwater, estuarine and marine ecosystems and the region’s economy. These crabs are catadromous—living in fresh water but migrating to marine and estuarine waters to breed. Juveniles can migrate upstream several hundred miles.

The Chinese mitten crab was first discovered in San Francisco Bay in the winter of 1992 and has spread widely through out the bay as well as the San Joaquin and Sacramento rivers. In 1997, a fisherman claims to have found a mitten crab in the Columbia River , although this sighting has not been confirmed. Mitten crabs were probably accidentally introduced in California in discharged ballast water or intentionally to start a fishery.

• What's the problem?
• What's being done in Washington State?
• Learn more

What's the problem?

Mitten crab burrows weaken flood-control levees and increase bank erosion. They are opportunistic feeders and will eat the eggs of salmon, trout and sturgeon and may even threaten spawning salmon. In California , they also eat rice crops in the Delta region and clog up screens used to protect fisheries at the point of water supply for municipal, industrial, hydroelectric and agricultural use.

One study suggests that Puget Sound has the ideal combination of temperature, salinity and other oceanographic conditions for mitten crab to become established.

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What's being done in Washington State?

The Puget Sound Partnership’s long range management plan calls on the state to develop an overall early detection and rapid response program. This program will find invasive species such as the Chinese mitten crab before they become problems and quickly respond to new invasions.