August 18, 2006 - A fisherman's recent discovery of a second Chinese mitten crab in the Chesapeake Bay has experts concerned that this invasive species could establish a resident population, endangering the already flagging native Chesapeake blue crab population.

The Chinese mitten crab is native to the coastal rivers and estuaries of the Yellow Sea in Korea and China. The species is already fully established in the San Francisco Bay, where it is believed to have arrived in a ship's ballast water. Scientists are trying to figure out how the mitten crab arrived in the Chesapeake, but say that so far there is no cause for alarm. The mitten crab faces several obstacles in establishing a resident population, including temperature variation and pollution.

A number of National Research Council reports have examined issues related to invasive species. Stemming the Tide: Controlling Introductions of Nonindigenous Species by Ships' Ballast Water explores strategies for reducing the likelihood of new introductions of aquatic nuisance species carried in ships’ ballast water. Nonnative Oysters in the Chesapeake Bay discusses the potential options for supplementing stocks of the native eastern oyster with an Asian oyster. Over the last 250 years, the native population has diminished to about 1 percent of its past abundance in the bay due to a combination of overharvesting and disease.

• Stemming the Tide: Controlling Introductions of Nonindigenous Species by Ships' Ballast Water (1996)
• Nonnative Oysters in the Chesapeake Bay (2004)

• California Dept of Fish and Game Mitten Crab Page
• USDA Invasive Species Page