Common Shore Crab

  • Common Shore CrabScientific name: Carcinus maenas
  • Also know as: Green Crab, European Crab
  • Size: 8-9cm across carapace
  • Distribution: Natural range is throughout Europe and this species is found in great numbers all around the British Isles. Also found elsewhere in the world as an invasive species.

Also known as the Green Crab and European Crab, the common shore crab is a species of crab which is found around all of Britain and Ireland’s coastlines. It is extremely common and is best known to anglers as an extremely effective bait in its peeler form an as a bait stealing pest when it is active and feeding in its natural environment.

Description

This species of crab grows to a maximum size of around 8 to 9cm across the carapace. Despite being known as the green crab the colour is highly variable and can be anything from brownish to green or red/orange. The front edge of the carapace has a serrated edge and eight legs and two claws are present. The claws are capable of delivering a mildly painful nip.

Habitat, Feeding and Behaviour

The common shore crab will be found wherever there is some rock or weed cover in water down to 100 metres deep.The common shore crab will feed on anything it can find. They will scour the seabed for any form of dead marine animals and will happily consume dead or rotting fish. The will also consume shellfish, marine worms or pretty much any other form of animal matter they come across, including other common shore crabs. Crabs become prey themselves with predatory fish such as cod and bass taking crabs, and large marine birds will also feed on crabs they find. The common shore crab must undergo a process of shedding its shell and growing a new one once or twice a year. During this vulnerable time the common shore crab is easy prey for predators and therefore hides itself away until the process is complete. It is during this time the crab is known as a ‘peeler’ and is of most use to the angler as bait. More information is available on the peeling process in the section on peeler crabs as bait.

Status as an Invasive Species

The common shore crab is native to Europe and the North East Atlantic and has a wide distribution stretching from Scandinavia and northern Europe, throughout the Mediterranean and along the northern coast of Africa. However, the common shore crab was found off the coasts of North America in the late 1800s, and since then has been steadily progressing its range around this region. This has been a major cause of concern to American and Canadian authorities, as this species has the potential to cause much damage to commercially valuable clam, mussel and scallop beds. The common shore crab can also harm other local (and commercially important) species of crab and lobsters by competing with them for resources. It is thought that the common shore crab is faster than many American species, and its more dexterous and powerful claws give it an advantage when competing for food. This pushes out local species and has the potential to vastly reduce their numbers. Common shore crab have also been confirmed as being present off the coast of Argentina, South Africa and Australia. It is believed that ships travelling from Europe and releasing ballast water may be a major cause of the common shore crab to foreign waters, while the importing of live lobsters may also play a role as common shore crabs can be present in the seaweed and gravel that the lobsters are packed in. The IUCN’s Invasive Species Specialist Group classes the common shore crab as one of the top 100 worst invasive species in the world and blames this species for the collapse of the soft-shell clam industry in both New England and Nova Scotia. They calculate that the common shore crab causes around $22 million of damage in the United States and Canada every year. The common shore crab is not widely consumed and is caught commercially in only very small numbers.

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