Invasive green crab destroys ecosystems. Is it a good thing that it is ending up on plates in New England?

Tens of millions of green crabs live in the waters of New England. The European native Carcinus maenas threatens native species and seagrass meadows. Since controlling its population is difficult, the idea of fighting the invasion with… a fork is gaining popularity.

European green crab in New England waters

The green crab is naturally found along the coasts of Europe and North Africa. It reached North America as a result of human activity, probably through maritime transport. It has been recorded on the eastern coast of the US since the 19th century. Today, large populations occur in New England, a region comprising six states in the northeastern part of the country, including Maine, Massachusetts, Connecticut and Rhode Island.

Carcinus maenas adapts well to a variety of environmental conditions. It tolerates significant changes in temperature and salinity, makes use of a wide range of food sources and has a high reproductive potential. A single female can lay up to 185,000 eggs.

Mussels and seagrass under pressure

The effects of the green crab are particularly visible among mussels, which Carcinus maenas feeds on. It also eats oysters and blue mussels. The species competes for food and habitat with native crabs and young lobsters.

Its impact on seagrass meadows is also significant. While searching for food, the crabs dig through bottom sediments and damage plants. The scale of the changes can be substantial. In Antigonish Harbour in Nova Scotia, a 95 percent decline in the area occupied by seagrass was recorded within one year and was linked to the green crab invasion. These meadows provide habitat for many species, stabilize the seabed and protect the coast from erosion.

Crabs also affect salt marshes. Disturbance of sediments can destabilize their edges and increase their vulnerability to erosion. The pressure exerted by Carcinus maenas therefore affects both organisms that are an important economic resource and coastal habitats.

From invasive species to food product

One idea for reducing the green crab population is to increase its commercial harvesting. Individuals during the molting period are particularly valuable. For a short time after shedding their shells, they remain soft and can be used in gastronomy as soft-shell crabs.

As Mike Masi, founder of shell+claw in Maine, explains in an interview with the Associated Press (AP, the American news agency), a soft-shell crab can earn around $3, while an individual with a hard shell is worth just 8 cents.

Restaurants create a market for green crab

Interest from the food industry is gradually increasing. According to AP, since 2021 the number of restaurants offering green crab has increased more than tenfold. These crustaceans are used in pasta, soups, sauces and sandwiches, and are also prepared in tempura. They are used to produce fish sauce and animal feed.

Market development is supported by actions taken by individual states. Rhode Island introduced a $10 license for commercial green crab fishing, while Maine created measures to facilitate its sale and processing. In some communities in Massachusetts, there are programs under which licensed fishermen receive an additional 40 cents for every pound of harvested crabs.

Insufficient infrastructure remains a barrier. Facilities for sorting, storing and processing crabs are needed, as is an efficient distribution system. An increase in harvesting alone will not be enough if there are no regular buyers.

Can consumption help control the invasion?

The mechanism seems simple: greater demand increases the profitability of harvesting, which may reduce the species’ population and its impact on the ecosystem. However, with a population numbering in the tens of millions, the current scale of efforts is too small to bring about a significant change.

The consequences of creating a permanent market remain an open question. If Carcinus maenas becomes a valuable commodity and its presence starts generating economic benefits, commercial interests may come into conflict with the conservation goal of reducing the population of an invasive species.

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main photo: CSIRO/Wikimedia