The good news here is that for pennies, we have an almost infinite local source for making crab risotto, etouffee, gumbo, soupe de poisson, cioppino and bouillabaisse, any number of wonderful fish dishes made especially delicious with local crab stock at a cost of almost nothing. More good news: The crab risotto you serve your family does the ocean a world of good.  

The bad news is that the source of all this goodness — green crabs, Carcinus maenas — is an invasive species that threatens, possibly on one hand’s number of years, to destroy shellfish beds from here to Canada. No more white cardboard boxes brimming with fried clams. No more plump steamers bathed in butter. No more wild mussels shining in white wine, parsley and garlic.

Carcinus maenas, native to central Norway, the Baltic Sea and a small part of Iceland, arrived here most likely as ship ballast as early as 1810. DNA tracing reveals subsequent invasions, maybe as ship ballast, or nestled into seaweed used for packing, or shipped aquaculture. Green crabs now make appearances around the world. They own the Eastern Seaboard as far south as South Carolina and as far north as Nova Scotia. They have infiltrated the Pacific coast from Baja, Calif., to Alaska, and as far as Australia, earning the dubious accolade as one of the 100 most invasive species in the world.  

At a green crab summit last year in Orono, Maine, Dr. Brian Beal, professor of marine biology at the University of Maine at Machias, declared that there would be no shipment of Maine clam stock for 2015, as green crabs had that much compromised Maine’s soft-shell clam beds. Our local Massachusetts market depends on Maine shipments, as there are not enough soft-shell clams dug here to supply the appetite for fried clams, clam fritters and steamers.

One green crab can eat 40 half-inch clams a day, or 30 small oysters. A half-acre wild mussel bed in Plum Island Sound, that locals considered an easy visit for a bushel of mussels, is gone, according to Rowley Shellfish Commissioner Jack Grundstrom. 

Green crabs also destroy native eel grass, a critical nursery for marine life, by burrowing into the mud, thus shredding the grasses at their base. Grundstrom actually points his 83-year-old finger right at green crabs for the collapse of the entire fishing industry, as these voracious beasts are devouring the food chain at its base.  

“Most of the food for the entire ecosystem comes from the North Shore’s Great Marsh,” he said.

The Great Marsh is the largest continuous stretch of salt marsh in New England, including more than 20,000 acres of marsh, barrier beach, tidal river, estuary, mud flat and upland islands across the North Shore, from Gloucester to Salisbury.

“Once that food is cut off, as green crabs are doing, all of our fishing culture is destroyed,” Grundstrom said.

Beal cites green crabs’ almost amazing tolerance for temperature and salinity fluctuations. Adult crabs can even live out of water for up to 10 days at summer temperatures. On the crustacean’s awesome vitality, Beal’s green crab paper, presented at the Maine summit, states, “Gregarious behavior encourages sexual encounter rates.” Green crabs reproduce like mad. 

Grundstrom explains a popular theory on why the green crabs, after making trouble for centuries, are now such a critical problem.  

“There had been a theory circulating for years that clams did very well after a harsh winter, believing that those hard conditions took a ‘skim’ off the mud flats, making it easier for the clams to burrow,” he said. 

Now, people believe that the clams did better after harsh winters because the green crabs didn’t, giving the clams a break for a couple of years.

The current theory is, according to Grundstrom, that a new strain of green crabs can withstand even lower temperatures. The new strain is crossbreeding with the old crabs and is able to survive harsher conditions. While some fishermen trapping crabs this year actually believe there really are fewer, because of last winter’s heavy toll, most people in the industry anticipate disaster ahead, and soon.   

Green crabs are currently being fished for bait. Ann Molloy from Neptune’s Harvest, the branch of Ocean Crest in Gloucester that produces fertilizer from fish products, said that currently the green crabs have too much sand in them for them to process.

“We tried, but they clogged our screens too fast,” she said. “At some point, if we open a crab shell drying and grinding plant here, we could take them all. We applied for a Saltonstall-Kennedy Grant for that, but we didn’t get it. We haven’t given up hope yet, and at some point, we’re hoping to still move forward with that project.”

State Sen. Bruce Tarr recently secured $133,000 from the federal government as an emergency stopgap measure for just this year, buying back green crabs from fishermen, thus assuring that someone will be catching them. But these measures aren’t enough at this point to control the population. The industry is looking for a market, a need, a great recipe for which the main ingredient is green crabs, a recipe that people will want to make often.  

Ideally, it would be great to have restaurants regularly making stock with these crabs. Until then, I’m sharing my crab stock recipe, with which I went on to make crab risotto with some great locally harvested celery, onions and peppers. 

This was honestly the most delicious stock I’ve made — sweet and complex, and loaded with a pleasant seafood flavor. I have 4 quarts of it in my freezer and can’t wait to cook more with it. The risotto made with the stock tasted authentically fresh and full of honest shellfish flavor, the kind of taste — with no exaggeration — I can attribute only to seafood dishes in Venice.  

For the record, Italians have been cooking with a relative of this crab for years; they’re considered a delicacy. We need to get these crabs into our stockpots.  

Green Crab Stock

Makes 6 quarts

4 tablespoons olive oil

2 bunches celery, with the leaves, about 1 pound, roughly chopped

1 large red onion, roughly chopped

1 small head fennel, cut into 1/2-inch slices

12 corncobs (optional)

2 bay leaves

Salt

1 tablespoon Old Bay Seasoning

Approximately 3 quarts water

2 cups white wine

2 dozen green crabs

Rinse crabs well in cold water. I recommend doing this outside in a large bucket; just fill the bucket with water and throw your crabs in. Stir well, and leave them in the bucket until your stock is boiling.

In a large stockpot or lobster pot, heat the olive oil to medium. Add the celery, onion and fennel.  Lower heat, and cook until vegetables are soft, about 15 minutes.  

Add the corncobs (if using), the salt, bay leaves and Old Bay, and stir well, tossing the vegetables well with the seasoning. Allow to cook for 5 more minutes, or until the onions just begin to darken.  

Add the water and wine, and bring to a boil. Let simmer for 10 to 15 minutes to integrate the flavors, particularly the corncobs.

Bring stock back to a hard boil. Bring the crabs into the kitchen, and scoop them into the boiling stock. Allow to cook at a strong, simmer-low boil for 45 minutes. 

Let cool, and spoon out the cooked crabs and as much of the vegetables as you can. Strain the remaining cooled broth through cheesecloth. Pour into jars or plastic containers for storing or freezing.

Green Crab Risotto

Serves 6

6 cups green crab stock

1 tablespoon butter

1 tablespoon olive oil

1/2 red onion, chopped

3 small carrots, diced, about 4 ounces

1 small banana pepper, or 1/2 a green pepper, seeded and diced

1 small red hot pepper, 1/2 ounce, diced (optional)

11/2 cups or 12 ounces arborio rice

Red pepper flakes

Salt and pepper

3 small tomatoes, seeded and chopped

1 pound crabmeat (1/2 to 3/4 cup reserved for garnish if you like)

Juice from 1 or 2 lemons or to taste

1/2 cup toasted slivered almonds

1/2 cup chopped fresh dill

In a medium saucepan, bring the stock to a simmer.

In a large saute pan, heat butter and olive oil together on medium heat. When butter is melted and bubbling, add onion, carrots and peppers. Let cook for 8 to 10 minutes over medium heat until softened. Add rice, and stir well, cooking until the rice begins to crackle and just begin to turn lightly brown. Season with salt, pepper and red pepper flakes.

Ladle in 1 cup of the hot broth into the rice, and stir until it is all absorbed.  

Add the chopped tomato, and then ladle in another cup of stock. Stir until the stock is absorbed, and then continue to ladle in the stock, stirring each addition until it is absorbed. This usually takes 20 to 25 minutes.

Taste the rice to make sure there is no “crunchiness” to it at all. You want it to be creamy, but not mushy. Stir in the fresh lemon juice and crabmeat. Serve in warm bowls garnished with the reserved crab, toasted almonds and chopped dill.