Invasive green crabs: If you can't beat them, eat...

Invasive green crabs: If you can’t beat them, eat them.


Published July 11, 2022

12 min read

West Bath, MaineIf you close your eyes, a green crab scuttling up your forearm feels more spider than sea creature, its little legs picking their way as if spinning silk. If you open your eyes, you will see the forged work of 200 million years: bumpy carapace, plated apron, calcified pincers. The small crabs are exquisite, seemingly carved from jade. The big ones are monstrous looking. They are nimble and chaotic, and likely under any beach rock in the Gulf of Maine.

But here, the European green crab is not native. It is an invader, a species that traveled to the region in the 1800s in the ballast water of trading ships. In the centuries since, the crabs have established a thriving population, feasting on soft-shell clams and blue mussels, overtaking fisheries that have sustained Mainers for centuries. Their monstrous appetites and canny ability to adapt and reproduce have outcompeted any efforts to remove them.

Now, one of the last defenses against these marauding creatures is not to eradicate them, but to eat them.

On a misty morning at low tide, Marissa McMahan, director of fisheries at the environmental nonprofit Manomet, and Jessica Batchelder, a research technician on her team, are counting green crabs, something they do three times a year, in the spring, summer, and fall. The count involves a square-meter PVC pipe contraption called a quad, a bucket for fleeing crabs, and sets of hands willing to be pinched as they plunge into seaweed in search of the snapping crustaceans.

At one point during the count, McMahan casually lifts a boulder to find a whole cast of green crabs squirming about, fighting each other to get out of her way. McMahan tosses several in the bucket, but some hurry away too quickly to be counted.

The goal of McMahan’s project is to count green crabs throughout the mid-coast region of Maine to help determine the feasibility of creating the first soft-shell green crab fishery in the United States.

Creating a crabby buzz

Ask any expert about the essence of a green crab and often you’ll get some curious responses. One expert calls them “wicked rugged.” McMahan says that their Latin name is the best descriptor: carcinus maenas, or raving mad crab. They’re aggressive and cannibalistic and will annihilate any species they share a space with, including each other.

Chef Ali Waks Adams uses an expletive to describe them and then says if they were the size of humans, the only species on planet Earth would be green crabs. They live in both warm and cold water; they can live out of water for a period of time; they reproduce like crazy. They are, to their core, the perfect invasive species.

They are in good company. The Gulf of Maine is heating up faster than 99 percent of the world’s oceans, a consequence of the warming Labrador Current, which has historically filled the gulf with frigid Arctic water, and the northward shift of the Gulf Stream, which brings with it warmer air currents and water. These two factors have presented Maine fisheries with plenty of obstacles, a primary one being an increase in invasive species. According to one report, at least 64 invasions have been documented in the Gulf, with more anticipated and possibly many others unaccounted for.

Aquaculture, trade, and climate change all play a role in the increase of invasives. Red and green algae, the common periwinkle, and the mouse ear snail all arrived to the Gulf of Maine the same way the green crab did. With the aquaculture introduction of non-native oyster species like the European oyster came several more destructive tunicates, including didemnum vexillum, which is also commonly referred to as sea vomit. While the timing of these species’ arrival varies, none would be present without humans, who drive these changes.

Invasive species live on both land and in the water. But non-native water species are harder to track and harder to demonstrate as having a negative effect on humans. To McMahan, however, the issue has always been clear. Coming from a family of lobster fishers (she is one herself), McMahan has been familiar with green crabs since her childhood in Georgetown, a town in mid-coast Maine. After becoming a marine biologist, she decided to focus her study on the invader she knew so intimately.

On the shore at the count, McMahan sets her sights on a cluster of rocks dense with seaweed, tosses the quad, and carefully navigates her way over to where it lands. She gently starts parting the knotted wrack inside the quad, exposing the barnacled rock beneath it, and methodically running her fingers over rock and seaweed. “There’s one!” she says, and detangles a grasping crab the size of a bottle cap from the briny thicket.

Creating datasets like McMahan’s is important for establishing how many crabs, and of what life stage, are in the environment. But when founding a fishery there is more to take into consideration, and the approach is often dictated by the species. Something like lionfish, which has a white flaky meat, makes for a good top-down approach because its analogues—cod or halibut—are already widely consumed. Put it on a menu, and people will bite.

The green crab is trickier and calls for creating a buzz. “One of the biggest challenges with creating a market for any invasive is … do you focus mostly on creating supply or do you focus on creating the demand? And how do you divide your effort among those two things?” McMahan says. Because green crab is a virtually unknown culinary entity, McMahan is concentrating on revving up interest. She’s reaching out to restaurant owners, chefs, and educators, introducing them to the crab’s potential as a main ingredient.

Then there’s the issue of regulations. Currently, there are none for fishing green crabs, but they could be required if it becomes a profitable fishery. Mike Masi, co-founder of Southern Maine Sustainable Shellfish, harvests green crabs with traps under a lobster and crab license so that he can sell them commercially. The former high school marine biology teacher started a small green crab operation that evolved out of one of his class projects; he sustains it with the help of former students. This summer, he is in his first commercial season and though he hasn’t met his admittedly ambitious goal of 3,000 crabs, he is about halfway there, which he considers a win.

McMahan’s and Masi’s plans are in their nascent phase, but both are convinced that Maine is the right place to be. Unlike the West Coast, which is just beginning to deal with the green crab issue and so is still focused on eradication, the Gulf of Maine population is well established and can’t be eliminated entirely.

“There are no drawbacks to tapping into a ridiculously abundant species that causes ecological harm,” Masi says.

There are green crab markets abroad, which is affirming, and the potential for a fishery does seem high. But critics say that eating invasive species is not an effective tool for culling them and will only spread the populations to different regions.

Getting over the fear factor

Both land and sea offer up invaders for consumption—a practice called invasivorism—though some are a tougher sell than others. Nutria, for example, 15-pound rodents resembling a beaver-rat hybrid, have established themselves in 16 states and feast on native plants along riverbeds, destroying entire ecosystems. They are primed for eating: You can smoke their meat and shred it or combine it with other invasives like tiger shrimp and Asian carp in a spring roll. But still, nutria hasn’t made it to mainstream cuisine.

Waks Adams works with McMahan to introduce green crabs to area diners by hosting pop-up tastings and working with restaurant owners to get the species on the menu. Waks Adams, who is currently a private chef but has run restaurants in the past, uses crabs in her recipes, and has a practical view of eating the invader. But she faces resistance. “How do you create a market for something no one is really looking for?” she asks.

The answer is in the preparation of the crab itself, which is tricky but tasty. Green crabs are generally small bodied, and not many reach six to seven years, when they are big enough to pick for meat. Other species, like blue or snow crab, are often eaten with tools to extract the succulent meat for dipping or mixing with breadcrumbs and herbs in a crabcake.

Green crabs are best when their shells are soft. At any phase of their lives they make an excellent base for stock, which Waks Adams is particularly enthusiastic about, and can be used to make a condiment akin to a fish sauce. In the restaurants Masi supplies with crabs, soft-shell green crabs are fried and served as sliders.

The preparation of green crab is, in large part, where McMahan’s data come in. One of the pieces of info she collects is how soft each crab’s shell is and how close it is to molting. Determining at what age and in what season green crabs have soft shells will help reveal when to harvest them.

To understand how international green crab fisheries work and how to prepare the crabs, McMahan traveled to Venice, where Mediterranean green crab has been on menus for hundreds of years, and sells for close to $40 a pound. There, the crab’s caviar is eaten in a dish called manzanetta, or battered and fried whole and served with lemon. 

Both McMahan and Waks Adams are realistic about the work it will take to really get a fishery off the ground, but they still see opportunity in the green crab. To some degree, it depends on diners and their comfort level with new foods. “I don’t think it’s the invasive part that gets people,” Waks Adams says.

But the newness in the U.S. of something like a green crab might be a big hurdle. The people inclined to eat green crabs are likely the ones who are already adventurously eating.

Restaurant buy-in is key

McMahan’s study will depend on long-term datasets that come from monitoring green crabs over decades. Though she recently received a grant from NOAA, funding can be intermittent. Free, open-source apps for citizen scientists, such as Anecdata, can help. With the app, users can count green crabs on their own and upload their data to McMahan’s project site. McMahan has been working on her project since 2016, but creating a fishery could take many more years to come together.

Restaurant participation is key. “I think we’ve seen the most success when we’re able to feature green crabs on the menu at restaurants that are willing to go the extra mile to learn about the issue, educate their staff, and provide information to their customers,” McMahan says.

But perhaps Maine has a head start in eating ocean invasives because of its reputation of being a seafood region.

“In my opinion, the beauty of cooking for other people is that you create these transient moments,” says Waks Adams. “When you use something that’s local and invasive and you’re saying this pot of cioppino is made with green crab and lobster and mussels and clams and all of these things grow together, and seaweed in the stock that came from the same moment … You’re capturing this time capsule.”

In some ways, the atmosphere has already been established. “Maine has a great culture of eating local, and an amazing reputation for seafood in general,” McMahan says. “So yes, it is a great place to eat invasives, particularly marine invasives.” 

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