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  • Writer's pictureAustin Pugh

Meet the Critters: European Green Crab

Juvenile green crab sitting on a rock
Carcinus maenas along the foreshore at Tomahawk, Tasmania, Author: Tim Binns, Source: Wikimedia commons

Critter Fun Facts: European green crabs are native to coastal Europe and were introduced to the North American Coast at some point in the 1800's by travelling in the ballast water of ships from Europe. After this time, they began expanding their range on both the east and west coast of North America's east. As green crabs expand their range, they began to bring destruction to more and more local ecosystems.

For example when introduced to an eelgrass ecosystem, they destroy eelgrass beds, which support socially, economically and ecologically important species like Pacific salmon and other young fish and invertebrates. Additionally, green crabs are very efficient at opening bivalve shells, creating strong competitive pressure on any native crabs and other native predators of mollusks. Often, green crabs outcompete native species due to their aggressive nature, resulting in negative ecological impacts. European green crabs have been seen along the coast of British Columbia's lower mainland, as well as across the Atlantic coast of Canada, and are predicted to continue spreading along the coasts due to their long planktonic larval stage. Green crabs spend 50-80 days in this planktonic larval state, giving them the ability to drift in ocean currents and populate new areas of the North American coastline unreachable to their adult forms. Additionally, adult green crabs can spend up to a week out of water, which provides time for them to be transported in boats, buckets, and fishing equipment.

Economic: European green crabs threaten economically important shellfish species through predation. There can also be a negative effect on the catch of native crabs and lobsters due to competitive pressure.

OA Impact: OA has a negative impact on the physiological health of this species when evaluating their ammonia levels, which can lead to higher stress.

Diet: The diet of green crabs varies throughout their 3 life stages. Planktonic larva are filter feeders, juveniles feed on detritus on the ocean floor, and the adult stage has a wide array of food items including: bivalves, snails, copepods, other crab species, other green crabs, marine worms, other small crustaceans, and many more. Green crabs are scavengers and have the ability to eat many animals but studies have show that their preferred prey are mollusks.

Habitat: Another name for the green crab is the "green shore crab" because of its habitat in near shore shallow waters. Due to their ability to withstand wide ranges of salinity and water temperatures, green crabs have a large geographic range and spread quickly. They can live in a multitude of substrates including rocky, sandy, marshy, eelgrass beds, and muddy bottoms. Green crabs can spend extended periods of time out of water and can often be found hiding in rocks or manmade items that are left near the shoreline.

Geographic Distribution: The European Green Crab is originally from Europe and North Africa, later unintentionally transported to North America via ships in the 1800's. Since this time the North American green crab population has continued to expand now reaching from Virginia to Newfoundland on the east coast and from California to British Columbia on the west coast.

To see an approximation of the green crabs North American distribution in Canada click here.

Linnaean Classification:

Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Superclass: Multicrustacea

Class: Malacostraca

Subclass: Eumalacostraca

Superorder: Eucarida

Order: Decapoda

Suborder: Pleocyemata

Infraorder: Brachyura

Section: Eubrachyura

Subsection: Heterotremata

Superfamily: Portunoidea

Family: Carcinidae

Subfamily: Carcininae

Genus: Carcinus

Species: maenas

European green crab photographed from the top down against a white background
Author: CSIRO Marine Research, source: Wikimedia commons

Etymology: The word Carcinus is derived from cancer = crab, the word maenas = A small sea-fish

Common Names: North Atlantic shore crab, harbour crab, green shore crab, green crab, European shore-crab, and common shore crab

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