The European green crab (Carcinus maenas) is an invasive species that has spread along coastlines around the world. This crab is known for its voracious appetite and ability to adapt to new environments. But what exactly does the green crab eat? In this article, we’ll take an in-depth look at the diet and feeding habits of this prolific invader.
An Overview of the Green Crab
- Native to the northeast Atlantic Ocean and Baltic Sea
- Has invaded coastlines across North America, South America, South Africa, Australia and Asia
- Features a distinct greenish color on its shell, but can also have red or yellow markings
- Grows up to 3 inches wide, with five spiny teeth on each side of its eyes
- Highly adaptable and can thrive in a wide range of habitats like salt marshes, estuaries and rocky shores
The European green crab was first introduced to the Atlantic coast of North America in the early 1800s. Since then, it has spread rapidly and caused major disruptions to coastal ecosystems. The green crab is now considered one of the world’s worst invasive species.
A Voracious and Opportunistic Feeder
The green crab is well known for its diverse and rapacious appetite. This crab will feed on a wide variety of prey species including:
Mollusks
- Clams, mussels, oysters, scallops, abalone
- Uses its strong claws to pry open shells
- Can decimate commercially valuable shellfish populations
Crustaceans
- Smaller crab species like rock crab, spider crab
- Cannibalizes other green crabs, including juveniles
- May outcompete native crab species for resources
Marine worms
- Polychaetes, ribbon worms, bristle worms
- Digs in sediment to find burrowing worms
- No match for the green crab’s strong claws
Fish and fish eggs
- Juvenile fish, fish carcasses
- Consumes eggs deposited on the seabed
- Further threatens populations of native fish
Algae and seagrass
- Consumes a wide variety of algae species
- Grazes on eelgrass beds, an important habitat for many organisms
- Could alter balance of vegetation in coastal areas
The green crab is known for targeting the most abundant or profitable food source in an area. When a new prey species becomes plentiful, the crab can quickly adapt and focus on this new food source. This allows green crab populations to grow rapidly.
Hunting Strategies
This opportunistic crab uses a variety of clever strategies to hunt down prey
- Actively pursues prey by patrolling intertidal zones during high tide
- Ambushes prey by burrowing and waiting for organisms to come within reach
- Uses sensory organs on its antennae to detect chemical cues from potential prey
- Leverages strength in its crusher claw to break apart shells and carapaces
- Employs persistence and will attempt to access prey over and over until successful
- Scavenges on dead and decaying animals as an additional food source
These varied hunting approaches allow the green crab to be highly successful across many different habitat types
Impacts on Native Species
The green crab’s voracious appetite and effective hunting techniques have major impacts on native species along invaded coastlines. Some of the most profound effects include:
- Declines in clams, oysters, mussels and other commercially-important shellfish
- Loss of seagrass beds and kelp forests due to grazing pressures
- Reductions in fish recruitment as eggs and juveniles are consumed
- Alterations to the community structure of tidal habitats
- Declines or local extinction of rare and endangered species
In areas where they have invaded, green crabs can quickly become the dominant species in the intertidal zone. Their feeding habits often displace native crabs as well. Researchers estimate that this single crab species is responsible for hundreds of millions of dollars in economic impacts each year linked to loss of shellfish harvests and damaged habitats.
Controlling This Hungry Invader
Scientists and resource managers are testing different techniques to control green crab populations and reduce their feeding pressure:
- Physical barriers such as fencing to exclude green crabs from sensitive habitats
- Trapping programs to directly remove crabs from invaded areas
- Development of commercial fisheries to harvest invasive green crabs
- Alteration of coastal habitats to favor native species over green crabs
- Public education to prevent further spread via recreational boating or fishing gear
Creating culinary markets for invasive green crabs is another promising control method. By developing appetizing recipes and products from green crabs, it may be possible to financially incentivize harvesting them from sensitive ecosystems. However, any commercial use would need careful regulation to avoid unintended consequences.
With its broad diet, effective hunting approaches and ability to adapt to new habitats, the European green crab has become a global menace. This voracious invader is capable of stripping native species from coastal environments across several continents. Understanding what the green crab eats provides key insights into how to manage this prolific invader. While controlling established populations is difficult, ongoing research and public engagement provide some hope for protecting ecosystems from the green crab’s appetite.
Search Search Fisheries and Oceans Canada
If you think you have found an aquatic invasive species:
- do not return the species to the water
- take photos
- note:
- the exact location (GPS coordinates)
- the observation date
- identifying features
- contact us to report it
Learn about European Green Crab, including its identifying features, location, habitats, impacts and our response.
The European Green Crab is native to Europe and North Africa. In Canada, European Green Crab has invaded:
- New Brunswick in 1951
- Nova Scotia in 1953
- The Gulf of St. Lawrence in 1994
- Prince Edward Island in 1997
- British Columbia in 1998
- The Magdalen Islands, Québec in 2004
- Newfoundland and Labrador in 2007
Although they look the same, there are different populations of European Green Crab found in eastern Canada. The first population spread into Atlantic Canada in the early 1950s, moving north from the eastern North Atlantic seaboard and are not cold tolerant.
A second population arrived in the 1980s and 1990s in northern Nova Scotia and are better suited to survive colder waters as they originated from populations in northern Europe. These 2 populations have mixed and reproduced forming a third cold tolerant hybrid population that is also rapidly spreading both north and south in Atlantic Canada.
Established populations of European Green Crabs have been found on the west coast of Vancouver Island. Since 2018, new detections of European Green Crab have been reported in:
- northern Vancouver Island (Port Hardy)
- southern Vancouver Island (Esquimalt Lagoon and Wittys Lagoon)
- the Gulf Islands (Salt Spring Island)
- Haida Gwaii
- southern British Columbian waters (Boundary Bay)
The European Green Crab (Carcinus maenas) is a small coastal crustacean. You can identify it by its:
- shell that:
- is serrated and pentagon-shaped
- has 5 sharp spines on the side of each eye and 3 rounded lobes between the eyes
- back leg tips that are:
- hairy
- pointed
- slightly flattened
- different sized front claws
- size, which can be up to 10 centimetres
- colour that varies from green to red or yellow
- temperament that is:
- territorial
- aggressive
If you think you have seen a European Green Crab, report it.
Nearshore native crabs found in Eastern Canada that look similar to the European Green Crab include:
- Rock Crab (Cancer irroratus), which:
- is larger (up to 15 centimetres)
- has a broad oval shaped shell that can be red/brown or purple
- has 9 rounded lobes on either side of the eyes
- Jonah Crab (Cancer borealis), which:
- is larger (up to 18 centimetres)
- has a scallop-shaped shell
- has 9 rounded lobes on either side of the eyes
- Lady Crab (Ovalipes ocellatus), which:
- has oval tips on its hind legs
- has 5 spines on either side of the eyes, like the European Green Crab
- is white to yellow/grey, with red/purple spots
Nearshore native crabs found in Western Canada that are green in colour and can be mistaken for European Green Crab include:
- Northern Kelp Crab (Pugettia producta), which:
- has a pronounced pointy nose
- has a shell that is longer (front to back) than it is wide
- Helmet Crab, also called Hairy Helmet Crabs (Telmessus cheiragonus), which:
- are covered with bristles and bumps
- has a diamond shaped shell
- Hairy Shore Crab (Hemigrapsus oregonensis), which:
- has 3 spines on either side of the eyes
- has a square shell
The European Green Crab are found near shore, usually in shallow waters less than 6 meters. They can tolerate a wide range of water temperatures and salinity (salt content of water). They are found in:
- salt marshes
- vegetation, including eelgrass beds
- rocky coasts
- sandy beaches
- sheltered areas
- shallow water on bottoms that are sandy, muddy or pebbled
The adult European Green Crab is very hardy and can survive out of water for 5 or more days. Its hiding places include:
- crates
- boats
- buckets
- fishing gear
- aquaculture gear
- equipment
The European Green Crab is highly resilient and can upset the balance of estuarine and marine ecosystems, impacting biodiversity. European Green Crab:
- live 4 to 7 years
- can eat a wide variety of plants and animals
- females can release up to 185,000 eggs once or twice per year
European Green Crab impact native ecosystems by:
- destroying beds of shellfish
- feeding on native animals, including:
- clams
- oysters
- mussels
- small fish
- juvenile crabs
- other crustaceans, including juvenile lobster
- out-competing native crab species for food
- disrupting eelgrass beds, which are habitats for many juvenile fish species
European Green Crab impact the fishing and aquaculture industries by:
- damaging eels when they enter the traps
- reducing the abundance of harvested species by:
- out-competing native crab and lobster for food and shelter
- feeding on shellfish, including juvenile lobsters, as well as small and juvenile fish
European Green Crabs likely arrived in North America around 1817 carried in the holds of wooden ships.
They are thought to spread during their long larval stage (up to 90 days) through shipping (ballast water transfers) or by drifting on ocean currents. They can also move from one area to another by hitchhiking unseen on boats and gear or in packaged shellfish.
Once European Green Crabs have established a population in an area, it is practically impossible to eradicate them. However, we can limit their spread and the damage they cause.
Fisheries and Oceans Canada is collaborating with many partners including:
- academia
- fish harvesters
- Indigenous Peoples
- conservation groups
- community members
- provincial and territorial departments
- the United States of America
We provide training on proper identification, sampling methods and data collection standards. Appropriate licensing to detect early invasions and to control populations of European Green Crabs are available in some areas. If your organization is interested in partnering, please contact us.
Where sustained removal of European Green Crab has taken place, the catch rate for these crabs has decreased considerably and native species have regained their territory.
Invasive green crabs aren’t going anywhere, so why not eat them?
FAQ
What is the best bait for green crabs?
Green crabs like some strange snacks. We’ve had luck with hot dogs, fried chicken, and mackerel bait.
What to do if you see a green crab?
If you find a suspected European green crab or its shell in Washington, take photos and report it as soon as possible using the form on the European green crab identification and reporting page. Review WDFW’s crab identification guide (PDF), and take pictures to confirm identification.
How do I keep green crabs alive?
- Container: Green crabs can survive for weeks out of the water. …
- Storage Time: Keep crabs in the fridge or comparably cool space and use them within 1 week.
- Smell: Frequently check the crabs for smell and remove any crabs that perish (a dead crab can spoil the whole bushel).
Are the green crabs in Maine edible?
Learn about the ecological threat these creatures pose to our state, but also about the proactive efforts underway to mitigate their impact. Plus, discover the culinary potential of green crabs and why they deserve a place on your plate – one way to help is to eat them!