European Green Crab

Carcinus maenas

Report it

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.

Identifying features

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 five sharp spines on the side of each eye and three rounded lobes between the eyes
back leg tips that are:
- hairy
- pointed
- slightly flattened
different sized front claws
size, which can be up to ten 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 fifteen centimetres)
- has a broad oval shaped shell that can be red/brown or purple
- has nine rounded lobes on either side of the eyes
Jonah Crab (Cancer borealis), which:
- is larger (up to eighteen centimetres)
- has a scallop-shaped shell
- has nine rounded lobes on either side of the eyes
Lady Crab (Ovalipes ocellatus), which:
- has oval tips on its hind legs
- has five 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 three spines on either side of the eyes
- has a square shell

Where is the species invasive

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 two 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 found on: northern Vancouver Island (Port Hardy); southern Vancouver Island (Esquimalt Lagoon, Witty’s Lagoon); the Gulf Islands (Salt Spring Island); Haida Gwaii and, in southern British Columbian waters (Boundary Bay).

Distribution

The European Green Crab is native to Europe and North Africa. It likely arrived in North America around 1817 carried in the holds of wooden ships.

European Green Crabs 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.

Habitat

The European Green Crab are found near shore, usually in shallow waters less than 6 metres. They can tolerate a wide range of water temperatures and salinities (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 five or more days. Its hiding places include:

crates
boats
buckets
fishing gear
aquaculture gear
equipment

Impacts

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

Ecological impacts

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

Socio-economic impacts

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

Response

Once European Green Crab 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
United States

We provide training on proper identification, sampling methods and data collection standards. Appropriate licencing 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.