Fighting invasive species in Southeastern Massachusetts
One of the most intriguing aspects of life along the shoreline is the feeling of perpetual mystery, the suspicion that for every perceptible phenomenon along the wrackline or among the tidepools, a multitude of unknown events transpires. Even a dry-shod lubber poking about in that border zone between land and sea is commonly treated to evidence of extraordinary happenings in the covert world beneath the waves: tracks of a diamondback terrapin where she crossed the dune to lay eggs, a pod of whales suddenly spuming and feeding in the bay, the remains of a poor mola mola, as flat and strange in death as it was in life, its body scarified by a cruel propeller. We coastal folks keep tabs on the creatures we care about, cheering on the victories—successful piping plover nest (yesss!)—and fretting over each harbinger of human-borne evil—the twisted carcass of an oil-fouled loon. We fight the urge, undoubtedly common in our Anthropocene Era, to tally these scraps of evidence into columns—the beauty and endurance of the natural world versus the ugly sum of human stupidity.
So that’s the background for me, turning over a bowling-ball-sized rock at the low tide line there on “my” stretch of Cape Cod Bay shoreline, and turning up something I’d never witnessed there before: an alarming flurry of frenzied scuttling. Suddenly a lot of unusual two-inch crabs were dashing for the cover of a nearby crevice, trying to wedge themselves in among—yikes!—another dozen small crabs already jammed under the next small rock over. My mind flashed to a story in The Boston Globe from a couple of years back. Something about an invasive crab—the green crab—destroying New England’s precious salt marshes, chomping up the spartina grasses and marauding the spawn of our native fish and shellfish. Is that what I had stumbled upon? I turned over a few more rocks, and it seemed as if hundreds of the furtive little critters swiveled their eye-stalks at me and skittered about my ankles, scrambling for cover.
Not all crabs are the same
Tamping down the instant assumption that this discovery simply could not be one for the plus column, I turned to the internet, as one does, to figure out how alarmed I should be. Among the usual trove of online tidbits and factoids, almost as scuttley and confounding as that crustacean horde, was incontrovertible proof, from the USGS, that my field identification was utterly wrong: green crabs these were not.
Rather, the compact, skittish lurkers I had disturbed were actually Asian Shore Crabs (Hemigrapsus sanguineus), pretty newly arrived in our neck of the woods. Turns out the more celebrated Green Crab (Carcinus maenas) is a bit bigger and flatter and less boxy than these fellows, looking overall like a murkier-colored junior version of the delicious blue crab found all-too-occasionally in our waters. But once I glimpsed the green crab’s mugshot, I knew that I had already been seeing it everywhere for years, blending in, acting aggressively casual, always solo so as not to bring on the kind of apocalyptic alarm occasioned by the skittering multitude of shore crabs, the “oh-my-god, we are completely overrun” feeling that motivates nativists everywhere. No, the green crab is the pale loner who feistily brandishes his claws and threatens mayhem, fearlessly flitting across the sand toward the massive human invader haplessly wading across his territory.
Invasives twice over
Everyone has heard the stories of human hubris and carelessness: plants and animals transplanted, knowingly or ignorantly, only to create havoc in every ecosystem but the one they evolved within. To get the origin story on New England’s green crabs, I turned to Roger Warner, founder and coordinator of the Green Crab R & D Project, a collaboration of myriad interdisciplinary partners based up the coast a piece in Ipswich, Massachusetts.
Apparently, green crabs have been transported to the coast of North America not once, but twice. Biologists postulate that the first wave of arrivals hitched a ride from southern Europe to the Chesapeake region as adult crabs clinging to fishing or other maritime gear in the holds of wooden ships around the time of the War of 1812. Yes, the darn things can survive out of the water, or in freshwater, for a shockingly long period, putatively the weeks it would take for a transatlantic journey in the age of sail.
This nineteenth-century green crab ancestor was said to be a shy and quiet little crustacean, but a shrinking manner and steady habits did not keep her and her friends from multiplying and spreading spawn up and down the Atlantic seaboard, ultimately mowing down populations of native creatures. By the mid-twentieth century, hungry green crabs were significantly diminishing human harvests of both soft-shell and hard-shell clams all around New England; the economic impact got the attention of folks who might not otherwise care about invasives, spawning initial studies. The situation only worsened in the 1990s when an angry new strain of green crab arrived from Scandinavia, discharged in ballast water from tankers while in the invisible larval stage of early crabhood. Soon after, biologists say, the two distinct European populations met and fell in love in some offshore nook, perhaps in southernmost Canadian waters, and their offspring proved to be not just more aggressive and short-tempered, but potentially more flexible about reproducing in a broader variety of water conditions. Behold: the scrappy modern green crab.
But what of Asian shore crabs?
When and how did they get to Cape Cod Bay? Turns out that they, too, employed the old ballast-water trick, likely arriving as larvae in the NYC shipping lanes in the late 1980s, shipped in from the coast of Korea or China or Japan. (Such ballast-discharge from tankers is now subject to strict regulation, incidentally.)
Two introduced species of crab, two entirely different MOs. But what they have in common, besides a tough exoskeleton and a bunch of pinchy feet, is a voracious, wide-ranging, adventuresome appetite and a terrific ability to reproduce. They swallow the larval forms of seemingly everything that lives in our waters, and they abrade the very grasses that define our marshes. Green crabs are even happy to eat each other (which may explain why they are such angry loners except when in love).
And, yes, both invasives are highly efficient breeders. The shore crab starts months earlier and ends months later than native crab species, producing three or four clutches of fifty thousand young at a throw. Even as mature crabs they are highly tolerant of crowding (I can attest!) piling cheek-by-jowl into tidal pools up and down the coast, squeezing out the locals like July tourists at your neighborhood bar.
By contrast, amorous green crabs retire with their sweethearts to a secluded deeper-water location for the purpose of egg-fertilization and incubation. The clouds of larvae they release offshore disperse widely, rapidly increasing their population distribution.
And there’s one last depressing kicker that applies to both invasive crab species. While the predators that eat our native crabs—including river otters, minks, seals, shorebirds, gulls, and diving ducks—take their toll on all crabs, regardless of origin, those pesky green and shore crabs somehow seem to have ditched their habitual parasites and other fungal and bacterial deadweight upon departing the old country, making them healthier than their cousins who stayed behind and our indigenous crabs to boot.
That means that both of these species arrived in our waters with a couple of advantages that my anthropomorphic side can’t help but characterize as grossly unfair to native crustaceans, who must now vie with these interlopers for habitat and diet.
A game plan—leveraging the marketplace
So what’s to be done about a super-robust population of small but ravenous omnivores now thriving on our shores, devouring all our favorite seafood in helpless infancy and destroying the vegetation which makes up the very fabric of the landscape? Since this is a food magazine, you probably know where this is going … as the most successful invasive species ever, we humans ought to be able to beat these invasives at their own game, and in delicious fashion.
A growing consortium of collaborators has not only been sounding the alarm about the destructive invasives but strategizing to employ our human advantages—science and culture—in order to drive down the numbers of crabby invasives by driving up our consumption of them. The green crab network includes fisherfolk, processors, and purveyors as well as research biologists; and encouragingly, restaurant cooks and cookbook authors, too, bringing in global crab-eating know-how. Their collective model urges calm, sensible action: keep your head, follow the crabs back to their homeland, and learn how the humans in that neighborhood make a meal of the little buggers.
Their multi-pronged approach offers a range of harvesting and marketing tactics designed to wipe out as many crabs as possible while providing nourishment for man, beast, and soil. Roger Warner of the Green Crab R & D Project laid out some potential uses of green crabs, arranged from high-value/high investment to low-value/ low investment.
Strategy 1: Green crabs as Venetian-style soft-shell luxury
Turns out that our transplanted southern European strain of green crab is part of a particular ancestral food tradition, pedigreed in the storied fishery of the Venetian lagoon. There the crabs are caught in traps from skiff s. Skilled individuals cull through masses of crustaceans to identify and sequester those on the verge of molting. Once shed of their carapaces, the soft-shelled green crabs (moeches, in Venetian dialect) are used in a number of knockout-sounding dishes, both traditional and contemporary. (One of the commonest recipes is a sort of a riff on the “final meal for the condemned” idea—the little crabs swim in a heavenly vat of seasoned beaten eggs, upon which, true to form, they busily chow down, stuffing themselves … so that you don’t have to. A quick dredge in flour, a couple of minutes deep-frying, and, presto! An irresistible dish of Moeches Fritti.)
Anyone who has ever eaten a soft-shelled blue crab knows how great an idea this is. That said, this most highly-evolved destination conceivable for an invasive species will probably never be a quick fix for the weekend crabber. Turns out it’s not too hard to catch a billion green crabs with a basic trap, BUT, learning to identify particular crabs that are working up to molting—that’s been the rub for New England watermen so far. Years of scientific research looking for a high-tech fix have so far yielded bupkus; meanwhile, on a YouTube video, you can watch an old Venetian hand as she tosses them into heaps of yeses and nos, passing judgment on each with a split-second squint. Exasperating and inspiring at the same time!
Several aspiring crab-molt-assessors have traveled from New England to Venice in the last few years to get some hands-on experience at the source, and this season Venetian moecante (green crab fisher) Paolo Tagliapietra is over here on Cape Cod, helping Jamie Bassett of Chatham learn to produce soft-shell green crabs for the market. That partnership has been facilitated by Marissa McMahan, Senior Fisheries Scientist at Manomet, Inc. Not only has she been coordinating connections among fisherfolk, but she is working with Gabbi Bradt, a biologist at the New Hampshire Sea Grant, to experiment with techniques forcing crabs to molt, which could potentially extend the green crab’s short soft-shell season to year-round.
Strategy 2: Green crabs as picked crabmeat
Green crabs, as I mentioned before, are structured like scaled-down blue crabs and when simmered briefly, yield meat as tender and sweet. The reward for the patient and meticulous picker (or better, multiple pickers) is just a wonderful treat in salads, fillings, garnishes, and soups.
Strategy 3: Essence of green crab as a cosmopolitan savory staple
This idea falls much lower on the spectrum in terms of the commitment, skillset, and investment required to get dinner. Essentially, it’s a way of converting whole crabs in any quantity into a deep flavor base for your cooking. You need a pot, a wooden spoon or another sturdy crushing implement, a strainer or colander, and a bowl or pot to strain into, all scaled to the volume of crabs at hand. Even lacking any seasonings at all, you can cover crabs in water and simmer until red, then break up shells as much as possible to extract flavor. (If you like you can add seasonings to resonate with the cooking you have planned.) Simmer again very gently 15 more minutes and strain. Use as stock for soups, noodle, and rice dishes. Chill to keep five days; freeze to keep three months. (See recipe, following, for details, elaborations, and variations.)
Strategy 4: Green crab destruction writ large
For those of us who are dedicated to the idea of conserving natural resources, responsibly gathering wild foods, and generally being the wise steward, it comes as quite a shock to be out to extirpate a species. It’s bracing to recall that every one of these crabs left in the water negatively affects the survival of our native clams, mussels, oysters, lobsters, and crabs (and pretty much every other living thing on the shore or in the water column). So I repeat the comforting mantra “Crush, Kill, Destroy” as I head out on my mission. Crabs that don’t go in my belly must be put to other uses. For example, they make great chicken or hog feed and enrich any compost heap.
On the macro-scale, this approach includes rendering crabs for commercial stock, pet food, and compost—objectives which have already been achieved at medium scale, according to members of the green crab research team. But Jeff Young, director of Advanced Marine Technologies, right here in New Bedford, told me that green crab falls into an awkward zone price-wise since his massive-scale processing operation is profitable largely by upcycling marine and other by-products. It’s a bit of a Catch-22 for the green crab: Jeff feels that since price tends to reflect its “highest and best use as human food,” he is unsure how the fishery could be structured to land these crustaceans purely to produce agricultural supplements, at least without subsidy. (It was interesting to learn that even though it’s unrelated to his actual business, Jeff happens to have worked with a local fisherman to process and ship green crab to test Asian markets with the product.)
Strategy 5: Support those who are already fighting the good fight
When your local restaurant offers curried green crab noodle soup or soft-shelled green crab po’boy or invasive crab paella, order a bunch for the table! Tell your friends about it. Go back next week and ask for it again if it’s not on the chalkboard. Your restaurateur and fisherfolk and those distributors who hold the middle ground will have gone out on a limb to offer this stuff—and it’s the excited, well-informed customer and her cash and word-of-mouth who ultimately makes their efforts worthwhile.
Local initiatives on the green crab front
A visit last winter by Green Crab R & D Project’s Roger Warner to the South Shore Science Center in Norwell may have spawned a few new local green crab initiatives right here on the South Shore and South Coast. After his standing-room-only talk, biologists, chefs, and commercial fisherman rubbed shoulders with seafood industry folk and plain-old concerned citizens, lining up to learn how to get involved in the effort. I overheard Kingston shellfisherman John Wheble talk about how he habitually nabs green crabs that cross his path and snaps them in half. He shrugged to acknowledge the futility of that gesture but was heartened to hear that there were efforts afoot to create a market and that he was well-placed to participate. Sharon St. Ours jumped in to see where her company’s marketing ties and infrastructure could fit into the mix. St. Ours & Co., her family’s Norwell- and Weymouth-based shellfish broth operation, already has the equipment needed to render large amounts of seafood into cooking bases friendly to consumers and food-service alike. I could see her gears turning as she started dreaming up new green crab products for both markets.
As spring sunshine warmed up the marsh mud and the green crabs began to emerge from their destructive burrows out into open water, I followed up with John and Sharon, and I learned that both of them had indeed been busy. Sharon is in the early testing stages of what will be a many-months-long process of green crab product development. To produce a single batch at the scale her equipment demands, though, she must first acquire thousands of pounds of green crabs—a great problem for fishermen like John Wheble to have. As of mid-May, he had just sold his first small catch—he’s been hesitant to invest in new equipment before he tests the market waters a bit—to John Nagle Co., the venerable Boston fish dealer.
Curious to learn where John’s catch went, I spoke to his shellfish buyer at Nagle, Paul Hagan. So far the demand seems to be largely Asian restaurants, and that’s what got Paul himself fishing green crab out of Duxbury, starting a visionary ten years ago. Now he sets 30 to 40 traps when he has time, landing five to six hundred pounds on a good day. Having been on the water all of his young life, he had seen the explosion in green crab numbers first-hand. When customers started asking for them, and he could find no one fishing for them, he knew a business opportunity when he saw it.
Paul’s perspective is that, as a species that needs to be hunted to extinction, green crabs have massive potential—a dream product for those whose business is otherwise thoroughly hemmed in bycatch limits. He is utterly confident that the project “is eventually going to pop off.” He sees the role of a persistent large-scale fish dealer as critical: “We’re the horsepower,” he tells me.
But what about those shore crabs?
While encouraged by all the good momentum on the green crab problem, I was left wondering about that multitude of Asian shore crabs setting up shop in my neck of the beach.
As much newer arrivals, the shore crabs have received considerably less attention thus far. Biologist Marissa McMahan told me that, yes, they had made their way up to coastal Maine, and that the anecdotal intelligence among the fishing community seemed to indicate that where shore crabs’ numbers were highest, the green crab population trended down. Upcoming surveys will tell.
Marine biologists at the University of Massachusetts at Dartmouth have been conducting studies on the shore crab and its ongoing invasion, learning about its habits as predator and prey, what native crabs it is displacing as it spreads around our shores, and what cues it to grow from a larva into a mature crab (which has got to be a helpful factor in understanding the molting process, catching the attention of cooks like me).
Academic work aside, I wondered how the green crab coalition’s hierarchy of destruction modes could be deployed as a template for shore crabs. I ticked through the potential items.
- Soft-shell shore crabs, if indeed a possibility, would surely turn out to be wonderful little mouthfuls, but would just as surely require huge expertise and infrastructure.
- Picking meat out of Asian shore crabs? No way—too teensy, no matter how delectable.
- Broth or bisque, using the same technique as with green crabs, cannot go wrong.
- Compost? Of course. Bound to be a bit smelly, but there’s no way that composted crabs won’t boost a garden.
So, broth it was, for starters. Then came the most surprising development. Out of the blue, my friend and neighbor Og Lim, a font of terrific treats from her native Korea, served up a shocker: a glistening plateful of aromatic shore crabs enrobed in a sweet chile sauce and flecked with sesame seeds! Apparently, when Og’s mother last visited from Korea, she too spied the little devils in a tidal pool and, recognizing them from their common home, gathered up a basketful and subdued them with frying and deliciousness. Og made note and many months later we were the beneficiaries.
Wow. A couple of those little guys with a glass of wine and I began to see the teeming crustacean horde as a boon rather than a threat. A bit like popcorn shrimp, but more juicy and flavorful; sort of like crawfish, but way crispier … This has simply got to find its way onto the chalkboard at everyone’s favorite neighborhood restaurant.
An unusual opportunity to restore ecological balance and provide economic opportunity
Once I started talking to people in New England’s invasive crab world, I was struck by just how much energy and creativity was being brought to bear on this problem from all sides. Clearly, the effect of all these folks’ clever work will be much broader and more meaningful than merely putting a dent in invasive crab populations. Biologist Marissa McMahan put it to me this way: these green crabs are just one opportunity, in these days of imperiled fishing stocks, for fishermen to diversify, while taking advantage of underutilized and overabundant species.
A fishing industry suffering from the twin ills of over-fishing and complex regulation needs individuals like these, who have an understanding of the fisheries and the market, whether their background is on the water or in the lab. Some of the scientists I talked to were both—they were raised in fishing communities, then pursued degrees in marine biology. Their respect for the fishing way of life is paired with a passion for restoring a strong ecosystem to support it.
By working directly with both the fishing community and the cooking community, and by alerting the public to their own delicious responsibility to eat these crabs, this group of biologists is placing themselves in an unusually public role as advocates and activists. To an outsider at least, that seems like not only a lot more fun than lab work but more rewarding in terms of making a positive economic difference in people’s lives and in restoring ecological balance on our coasts.
At this particularly perilous moment in environmental history, when each day seems to pile a few new items into the negative column, it’s truly heartening to learn about humans using their powers for good.
The Green Crab Cookbook, by Mary Parks and Thanh Thái. A guide to the network of green crab suppressors as well as a terrific compendium of globally-inspired recipes. The instructive illustrations and text will save the beginning crab-cook from wasting oodles of time reinventing the wheel. Available at: www.GreenCrab.org/cookbook
As we go to press, the cooking staff at several of our favorite establishments are expressing interest in plating these crabs for you. Keep an eye on the specials boards as the weather heats up!
Local seafood broths and powders from St. Ours & Company
European green crabs sport five lateral spines along the front end of the carapace (shell) on either side of the eyes; three bumps between the eyes. Carapace width: 6 -10 centimeters. Before you harvest green crabs, the Massachusetts Division of Marine Fisheries asks you to have a letter of authorization. Call 617-626-1633 or email email@example.com.
Asian shore crab have a squarish shell with three spines on each side of the carapace. The carapace color ranges from green to purple to orange-brown to red. It has light and dark bands along its legs and red spots on its claws. Male crabs have a distinctive fleshy, bulb-like structure at the base of the moveable finger on the claws. Carapace width: 3.5 – 4 centimeters.
*This story comes to us from Edible South Shore & South Coast. Paula Marcoux turns over rocks and eats what she finds underneath in Plymouth, Massachusetts. She is the author of Cooking With Fire. Photo: Thanh Thái and Mary Parks of the Green Crab R & D Project, photo by Roger Warner, founder and coordinator.