Wednesday, December 19, 2007

Chinese Mitten Crabs

Another Chinese mitten crab was found in the Hudson River, this one up near Cold Spring. The Hudson River Almanac has details, and characterizes the find rather dramatically: “…it casts an ominous cloud on the estuary.” (That must be one big crab.) Here’s what the Almanac says:

It was announced this week that a second Chinese mitten crab, this one an immature female, was recently found along the Hudson. Coupled with the first recovery this past June, it casts an ominous cloud on the estuary (see 12/9 Cold Spring). …

12/9 - Cold Spring, HRM 54: This past October 29, a second Chinese mitten crab was found at the Cold Spring Boat Club boat launch (see 6/3 Nyack for the first mitten crab, an adult male). It was confirmed as an immature female, 30 mm carapace width. The juvenile female mitten crab was brought to the Smithsonian Environmental Research Center in Edgewater, Maryland, in early November. Although we now have 11 confirmed mitten crabs from the Mid-Atlantic region, this is the first appearance of a juvenile. Yet, we still cannot confirm a self sustaining population. Continued monitoring is needed to establish a better understanding of the population.
- Carin D. Ferrante, Amanda Higgs

[The Chinese mitten crab (Eriocheir sinensis) is native to the estuaries of China where it is highly regarded in the market. Mitten crabs are catadromous, meaning that they spend much of their life in freshwater, then return to higher salinities in the lower estuary (15-20 parts-per-thousand salt) to reproduce. The salinity gradients of east coast estuarine systems like the Chesapeake Bay, Delaware Bay, and the Hudson River are nearly ideal for them. Adult mitten crabs have a carapace width of about 3", but six of its 8 legs are almost twice as long, giving them an almost "spider crab" look. Unlike the native blue crab, a swimming crab, mitten crabs are burrowing crabs, similar to our mud crabs only many times larger. They have a generalist diet, varied in prey, and their potential ecological impact on east coast estuaries is still unknown.

Chinese mitten crabs were inadvertently introduced to Europe in the 1930s and are now widespread. The first U.S. mitten crab was caught in San Francisco Bay in 1993, though they may have been there earlier. They first appeared along the Atlantic coast in Chesapeake Bay in 2005. One more followed in 2006, and another this year. Already, 4 mitten crabs have been collected from Delaware Bay this year. All 7 of these crabs, plus the earlier one from the Hudson, have been males.

Chinese mitten crabs have been an invasive species in Europe for a decade or more. The Marine Invasions Lab at the Smithsonian Environmental Research Center in Edgewater, Maryland, is working with U.S. Fish and Wildlife Service, NOAA, and the Maryland Department of Natural Resources in monitoring their presence. It is illegal to import mitten crabs into the United States, but there is genetic evidence that the east coast mitten crabs arrived here from Europe via commercial traffic, much like zebra mussel in 1988.

If you encounter a mitten crab in New York State, please notify Leslie Surprenant, NYSDEC Invasive Species Management Coordinator (518) 402-8980, (, and Carin D. Ferrante, Smithsonian Mitten Crab Coordinator ( Do not release them alive! If you take photos, make certain that you take both dorsal and ventral - top and bottom - views so we can determine its sex. Leslie Surprenant.]

Compiled by Tom Lake, Hudson River Estuary Program Naturalist New York State Department of Environmental Conservation.

And here’s more info about the Almanac itself, which is a great thing and should be duplicated on Long Island Sound:

The Hudson River E-Almanac is compiled and edited by Tom Lake and emailed weekly by DEC's Hudson River Estuary Program. To sign up to receive the E-Almanac (or to unsubscribe), send an email message to and write E-Almanac in the subject line.

Weekly issues are archived at

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