You Ought To Tell Somebody: (4) Chinese Mitten Crabs

Narrator: one potential new invader that particularly threatens the Pacific Morthwest is  the chinese mitten crab. Its history in California provides a case study of a very harmful invasion -- and one that the nearby states of the northwest should prepare themselves to prevent.

Named for the hair-like patches on their claws, these mitten crabs move fast and far. They foul fishing gear, steal bait, clog water systems, and may carry human parasites.

In 1992, commercial shrimp trawlers in San Francisco bay were the first to find this Asian native on the west coast.

Their numbers - low at first - increased at an alarming rate.   Today, california shrimpers sometimes remove hundreds of crabs from their nets in a single trawl.  How did chinese mitten crabs get to california?

Kim Webb: The two most likely methods of introduction would be ballast water releases from ships or intentional release by people to establish a fishery as a food source.

NARRATOR: An Asian delicacy, live mitten crabs have been sold illegally in California markets for more than fourteen dollars a pound.

Shipping probably led to their arrival in Germany in the early 1900's. By the 1930's, mitten crab had spread throughout most of northern Europe, fouling nets, mangling fish and causing major economic damage to commercial fishing operations.

Next: (5) Mitten Crab Life Cycle