As the weather turns warm and people begin boating, fishing, crabbing and exploring the Hudson River, the New York State Department of Environmental Conservation (DEC) has reissued its alert for the Chinese mitten crab for the entire Hudson River Estuary.
What is a Chinese mitten crab?
According to the DEC, the Chinese mitten crab is the newest invader in the Hudson. The crab, a native of southeast Asia, is an invasive species that arrived on the east coast in 2005; the first confirmed record being in the Chesapeake Bay near Baltimore.
And in 2007, the first specimen was discovered in the Hudson River by a commercial crabber working near Nyack.
“Mitten crabs were caught in the Hudson as late as last September," said Darrick Sparks of the Smithsonian Environmental Research Center in Maryland. "There have been no 'confirmed' records this year. Yet.”
How did these creatures reach our shores? According to Dr. Robert Schmidt from Hudsonia Ltd., a non-profit research institute in Annandale, “It is likely the crabs were introduced from the ballast water of ocean liners or freighters, but the possibility exists that they were a live release. In some Asian countries, the species is considered a culinary and medicinal delicacy—its eggs are thought to be aphrodisiacs. The Smithsonian people are trying to figure out (using DNA) which is scenario is most likely.”
"All we know is that they’re here and they’re posing a potential threat to the river’s ecology,” he said.
When asked if, judging from the sampling data, there exists a viable breeding population in the Hudson Schmidt replied, “Absolutely. We have seen new young every year of the past three years.”
What makes these animals such a menace?
Schmidt, who has been studying the Chinese mitten crab in the Hudson since the first specimen was discovered noted that the "animal's burrowing activity has the potential to seriously erode the banks of streams, rivers and levees and undermine the integrity of river side structures such as docks, railroad tracks and bulkheads. Such activity also leaves the riverbanks more prone to flooding.”
“Also they may, due to their aggressive nature, overtake other aquatic species, especially the native blue crab, a species that is fished commercially in the river," he said. "We don't know how they will interact with blue crabs but if they get as abundant as they have in Europe, it could change the ecosystem quite dramatically.”
The crabs are mainly freshwater dwellers that migrate back to salt water to breed. They are capable of walking on land and can maneuver around obstacles such as dams. Specimens have been found far up tributaries to the Hudson mainstem.
How can one identify this invader?
The DEC describes the Chinese mitten crab as “light-brown to olive in color. Adult mitten crabs have two hairy claws (or "mittens") with white tips. Their body, or carapace, is round and smooth and usually no larger than 4 inches wide. They have eight sharp pointed walking legs; no swimming legs, and a notch between the eyes.”
What should you do if you see or catch a Chinese mitten crab?
According to the DEC you should never release it back into the water! You should keep it and freeze it, or preserve it in alcohol if freezing is not an option. Make note of the location, with GPS coordinates if possible. Record the method of catch and take a close-up photo if possible.
Send the information to:
NYSDEC Office of Invasive Species Coordination
Albany, New York 12233-4756
Or to the Smithsonian Environmental Research Center:
Notes the DEC:
NYS Fish and Wildlife regulations (Section 44.10) prohibit releasing Chinese mitten crab into waters of New York State; prohibits possession, importation, transportation, purchase or sale or offer of purchase or sale of Chinese mitten crab whether dead or alive. This regulation requires Chinese mitten crab to be destroyed unless lawfully held under a license or permit to collect, possess or sell for propagation, scientific or exhibition purposes issued under section 11-0515 of the Environmental Conservation Law. In addition, the Federal Lacey Act prohibits interstate transport of Chinese mitten crabs.