Marissa McMahan: Invasive green crabs are scuttling from dilemma to delicacy
Photo: Jonathan Taggart

Marissa McMahan: Invasive green crabs are scuttling from dilemma to delicacy

Posted by Lauren Hertel on Monday, September 5 2016


Editor's note: The following story and accompanying video first appeared on The Portland Press Herald's website.

A marine biologist, an art conservator and a group of fishermen from Georgetown are trying to use traditional Venetian fishing methods to turn the invasive green crab into a gourmet dish known in Italy as moleche.

Moleche is the name of the young, soft-shelled Venetian crabs that are caught, sorted and held in floating cages and harvested daily, right after they shed their hard outer shell. They are dipped in milk or egg, floured and fried, served up six or eight at a time for about two dozen euro in upscale eateries across the Veneto region of Italy.

Their nearly identical American cousins are reviled in Maine for decimating clam flats and threatening the state’s $23 million industry, as well as preying on other mollusks such as mussels and scallops. They can be caught with nets or traps, including the shrimp traps that now lie fallow here in Maine.

The real art of the moleche (moe-le-che) fishery, however, is about spotting the subtle signs of a molt about to happen in time to catch them before they hide or are eaten by a predator, including their fellow crabs.

Scientists at the University of Maine at Machias had studied the moleche possibility of the green crabs once before, and concluded the crabs did not give any external clues to their molts and thus could not be harvested commercially. But as the invasion marched on, and efforts to eradicate the crab failed, scientists on Prince Edward Island decided to give it a second look. So did marine biologist Marissa McMahan, a Northeastern University Ph.D. candidate from a Georgetown lobstering family who lives in Phippsburg.

McMahan applied for and got a $3,000 Maine Sea Grant to study the moleche potential. She and Jonathan Taggart, the art conservator who brought the moleche tradition to McMahan’s attention, and a small group of Georgetown lobstermen began to trap the green crabs in Robinhood Cove and Five Islands Harbor to collect data on population, size, gender and molting. They were hoping to learn if these two closely related crabs – same genus, different species – had enough in common that the Venetian fishery could be duplicated here in Maine.

“There is no one thing that will solve the green crab problem,” said McMahan. “But a soft-shell market could, when taken together with other methods, help slow down the population growth of the invasive species, and maybe, over time, give us a new market for Maine fishermen to do to diversify the industry. As a state, we can’t just rely on lobster, because a one-fishery market, or economy, is dangerous, especially with the warming ocean temperatures. We may not have a huge impact, not right away at least, but if this works, it would be a step in the right direction.”


Originally from Europe, the green crab, or Carcinus maenas, reached America in the mid-1800s after riding across the Atlantic in the ballast water on ships. They have been in Maine for more than a century. They live in the shallows and the soft-bottom and rocky sections of the intertidal zone.

As the water temperature rises, the crabs are proliferating, and have been eating their way through East Coast mussels, clams and eelgrass beds, and undermining salt marshes with their labyrinthian tunnels. Over the last decade, efforts to eradicate the invader, from creating bait markets to volunteer and town-fundedharvests, have failed.

Despite the crabs’ abundance, the Georgetown group quickly learned, like others before them, how difficult it is to identify a pre-molt green crab. Unlike the Chesapeake blue crab, whose swimming fins will turn pink, then red, as a molt approaches, the green crab’s molting signals aren’t easy to detect.

That is when Taggart, the Georgetown conservator who had learned about the moleche tradition on a recent trip to document the wooden boat tradition in Venice, agreed to go back to Venice to ask the molecante – the Italian word for soft-shell green crab fishermen – for help learning how to sort and cultivate these crabs.

Taggart invited Paolo Tagliapietra, the 36-year-old molecante whom he had met on his trip, to come to Maine to share this centuries-old fishing tradition. One of the youngest crab fishermen in Venice, Tagliapietra is worried the moleche tradition may be fading. The dish remains highly prized, but fewer and fewer young people are joining the ranks of the molecante. And he knows better than most just how much skill, and experience, is needed to identify a pre-molt green crab.

So Tagliapietra bought his own plane ticket to come to Maine to teach what was essentially a two-week crash course on moleche fishing to the Georgetown group as a way to preserve and maybe even expand the molecante tradition and help diversify the Maine fishery.

Tagliapietra said he came here to help his new friend, Taggart, better the lives of local fishermen. Others have asked him to teach them how to fish for the green crab, and he has refused. But as a fisherman, he wouldn’t turn away a request to help other fishermen overcome a problem.

And he believes that the moleche tradition, which he learned from his grandfather and father, both of whom spent their whole lives perfecting their skills, could work in Maine.

“I really think that there is the possibility to have soft-shell crabs like in Italy,” Tagliapietra said. “Probably a simple cut and paste of our technique isn’t enough. There are for sure some things to adapt and learn, but the base is the same. (It) is not a start from zero, at all.”


The Venetian green crab molting season occurs twice a year, in the spring and fall. Small numbers molt at other times of the year, and those crabs fetch higher prices for the fishermen because of their limited quantity, but it’s in March, April, October and November that moleche fetch about $20 a pound in the Venetian fish markets.

It is too early to tell if the Maine crabs will follow the same molting season, or if the different length of day and water temperature will alter the shedding calendar slightly for the green crabs that live in Maine.

Tagliapietra taught the group how to spot a pre-molt crab. It isn’t molting season now, but every one of the handful of green crabs that Tagliapietra found that he labeled as an out-of-season pre-molt ended up, in a matter of days, emerging from its exoskeleton, clad in a fragile, gelatinous new shell.

It suggests that Maine fishermen, already trained to note small changes in a fishery, could learn to identify pre-molting green crabs, or what Venetians call grancia buono, and catch them before they go into hiding, where their shells will thin, turn gray and be replaced in a day or two.

“We have much to learn, and much work to do, but as Paolo says, there is potential!” Taggart said.

Young crabs molt more frequently, and are usually greener in color than older crabs, which take on more gray, brown or red hues. According to Tagliapietra, the first signs of molting can occur up to three weeks ahead of time, with a fine white line developing on the edge of the plates found on the underbelly of the crab, followed by a darker shadow. The carapace, or the back of the shell, will begin to gray. The shell will soften, especially where the tail meets the carapace. Then the underside of the body will become opaque. When the crab grows lethargic, molting is imminent.

“The signs can be extremely hard to see in bright sunlight, so they are looked for in the shade,” Taggart said. “It helps to wear some good magnifying glasses!”

Tagliapietra urged the group to consider building another green crab market called masanete. These are the pregnant females carrying eggs that can be harvested in the fall, and are far easier to identify, and are usually boiled and seasoned with olive oil, parsley and sometimes garlic and often served over pasta. Harvesting these pregnant females, which can carry up to 185,000 eggs at a time, would cull future generations of this invasive species while providing a diversified source of income for Maine fishermen.

The Georgetown research group is easing up on its sorting work now, and just collects the basic population information from its traps, but will restart the molting work in late September, before the fall shed is likely to begin.

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