A Chinese mitten crab was first collected in South San Francisco Bay by a shrimper during the winter of 1993. MSI brought one of these crabs to the California Academy of Sciences where it was identified by Dr. Bob Van Syke. The discovery of the mitten crab in San Francisco Bay caused a big stir. Although mitten crabs had previously been found elsewhere in the U.S., San Francisco Bay was the first place where the crab could feasibly reproduce and increase its numbers.
Mitten crabs are native to mainland China and coastal areas along the Yellow Sea.
They are catadromous, meaning they grow and develop in freshwater and then travel to saltwater to reproduce and die. Mitten crabs were introduced into German waters during the early 1900's, most likely via ballast water carried on large ships coming from China. The crabs did very well in German waters and quickly expanded their range outside of Germany. Mitten crabs were a big nuisance in Germany and elsewhere during the peak of their invasion. Large numbers of burrows excavated by the crabs caused problems with bank erosion and levee damage.