Crab species invades waters
Edwin Rodriguez has hauled in all manner of oddities in his 17 years as a fisherman for Copps Island Oysters in Norwalk.
So it was a shock when, in December, he pulled up an oyster grate in the Housatonic River between Stratford and Milford to find something totally new: a crab about the size of a human palm with long, skinny legs and furry “mittens” on its claws.
“I’ve been fishing all over Long Island Sound and I’ve never seen one of those crabs,” Rodriquez said. “I took a picture and sent it to my boss. I said, ‘I’ve never seen one like this. What is it?’ It was weird for me.”
Dick Harris, a marine scientist for Copps Island, identified the crab as the highly invasive Chinese mitten crab — named for those furry claws — and immediately sounded the alarm.
The crabs are native to China, where they are considered a delicacy in Asian cuisines, but for nearly a century they’ve occupied other locations as one of the top 100 invasive species in the world.
They migrate up freshwater rivers from saltwater bays and burrow into the banks — destabilizing shores, weakening dams and levees, clogging screens, pumps and water intake structures and causing hundreds of millions of dollars in infrastructure damage. The crabs have destroyed riverbanks in Germany and parts of the United States already.
They’re also resilient like rats, with a proven ability to survive even in polluted waters. They’ve wreaked havoc on recreational fishing industries by consuming bait, damaging fishing nets and devouring catch.
And to top it off, they’re a threat to human health, carrying a number of harmful bacteria and a parasite that attacks human lungs if the crabs are eaten raw or undercooked.
Now, suddenly, they’re threatening Connecticut’s shores.
“They burrow in by the millions and turn the bank into jelly,” Harris said. “It’s potentially a huge problem and we should be really worried about it.”
Rodriquez has found six crabs — five males and one female, all of reproductive size — since December. Most recently, he pulled up three on June 2. A single female can release up to 1 million eggs.
“I would probably now call this an invasion rather than an introduction,” said Dave Hudson, a research scientist at the Maritime Aquarium in Norwalk. “We need to have our eyes on the water when it comes to these things. An animal like this can be pretty devastating economically.”
Operation Hidden Mitten
Usually enjoyed steamed, with a light dipping sauce of minced ginger and garlic, mitten crabs are in highest demand in the fall, when they’re easiest to catch.
While you can get them live from a vending machine in China, the crabs are illegal to possess and illegal to serve in restaurants in the U.S., and it is illegal under the Lacey Act to import mitten crabs into the United States.
But that hasn’t stopped smugglers from bringing thousands to the U.S. every year for Chinese New Year and other cultural events.
In January, officials from the U.S. Fish and Wildlife Service announced they’d intercepted illegal shipments of approximately 15,000 live Chinese mitten crabs as part of a codenamed operation called “Hidden Mitten.”
Operation Hidden Mitten was the first international inspection operation initiated by the newly formed U.S. Fish and Wildlife Service Wildlife Inspection Interdiction Team, the agency said in a release in January.
With the assistance of U.S. Customs and Border Protection, wildlife inspectors found the crabs in boxes falsely marked as shipments of T-shirts, jeans, auto part samples, shopping bags, photo albums and other commercial products, the agency said.
Investigators seized the crabs at hubs and major international airports, and intercepted more than 3,400 pounds in Cincinnati alone. The shipments originated in China and Hong Kong and were destined for residences and businesses in multiple U.S. states. Most were headed to New York, federal officials said.
“The U.S. Department of the Interior is committed to protecting our nation’s natural resources for the continued benefit of the American people. Chinese mitten crabs pose a significant threat to humans, the environment and our economy,” said Rob Wallace, assistant secretary for Fish and Wildlife and Parks at the U.S. Department of the Interior, in a prepared statement.
Connecticut has crabs
It is unclear how the crabs ended up in Connecticut — though there are several theories. Often, the thrifty critters are scooped up in the ballast water of ships and released when the ship reaches the next port.
In many places, the crabs are illegally imported and then intentionally released to create a local supply for seafood markets. And there’s always a risk that one of those boxes of “Tshirts” could fall off a ship during transport.
Mitten crabs also aren’t the first out-of-towners to turn up in Connecticut waters. Fishermen from Copps Island found four Dungeness crabs in 2017, though they tossed three back. They took the fourth, a 2.5 pounder, to the Maritime Aquarium, where it was identified as one of the crustaceans made famous by the Discovery Channel’s “Deadliest Catch.”
They are native to the icy waters of the Pacific and none have been found in Long Island Sound since, so it’s unlikely they’ve survived or taken hold here.
In 2018, a single mitten crab was found in New Haven, but when no more were pulled up it was thought to be an isolated incident.
Now, though, mitten crabs are more likely to take hold, Harris said, and that could be costly for the state both in the damage they can cause and the expense of fighting them. Recent studies estimate the economic cost of combating invasive species in the United
States is approximately $120 billion per year.
Master escape artists
In the United States, mitten crabs have already spread to several California waterways, the Chesapeake and Delaware bays, and the Hudson River, according to the fish and wildlife agency. The crabs can migrate up to 11 miles per day on land and water, have been found as far as 8 miles upstream in some areas and are capable of climbing even the steepest walls — something Harris found out the hard way.
He placed the three most recent stowaways in a glass tank at the lab he keeps at Copps Island Oysters. The next day, he came in to find an empty tank. The crabs had escaped. He found them crawling around the house, scooped them up, placed them back in the tank and covered it with a board.
Even that didn’t work. They were gone again the next day. One made it all the way to the basement. He didn’t find the crabs in time, and now he keeps them in the freezer.
So the master escape artists have already proved they won’t be easy to contain if they multiply in Connecticut’s rivers, Harris said.
Harris and Hudson said recreational and commercial fishermen should be on the lookout for crabs with furry claws, and if you find one, contact them immediately, as well as the state Department of Energy and Environmental Protection. Harris is working with the department to gain approval to set a trap for the crabs.
Both Harris and Hudson were clear: If you catch one, do not put it back in the water.
“If it looks like it has hairs on its claws, it is not native,” Hudson said. “If it has hairy claws, I want to see it.”