What are Chinese Mitten Crabs? (Eriocheir sinensis)
They’re not there… yet.
But if Chinese mitten crabs make their way in to the Puget Sound, they could pose a serious threat to fresh water, 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.
When was this crab discovered?
This type of 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 Colombia River, although this sighing has not been confirmed.
Mitten crabs were probably accidentally introduced in California in discharged ballast water or intentionally to start a fishery.
What is 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.
One study suggests that Puget Sound has the ideal combination of temperature, salinity, and other oceanographic conditions for mitten crab to become established.