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European shore crab (Carcinus maenas)

The European shore crab is an invasive predator established in parts of southern Australia and listed on the Australian Priority Marine Pest List. It can prey on native species and damage shellfish fisheries and aquaculture.

Key facts

Type: Pest animal, invertebrate.

Native to: Atlantic Europe and possibly north-west Africa.

Established in: NSW, VIC, TAS, SA.

Other names: European green crab, green crab.

Best time to act: Warmer months are generally more suitable for trapping, as crabs are less likely to enter traps in winter.

Identification

  • It has a broad, roughly triangular carapace with five marginal spines on each side.
  • Colour varies from pale green through orange to deep red-brown, often most evident on the underside and limbs.
  • Its legs are robust, with flattened, pointed tips; the fourth walking leg has no swimming paddle.
  • The carapace can reach about 9 cm wide.
  • Look-alike: The related crab Carcinus aestuarii can look similar; in males, its pleopods are straight and parallel, while those of C. maenas curve outward and touch, though this can be difficult to assess in the field.

Where it lives

In Australia it lives in intertidal and shallow subtidal habitats, especially sheltered bays and estuaries, including seagrass, soft sediment and other sheltered areas.

Why it matters

  • It preys on native molluscs, crustaceans and other fauna, and can compete with native species for food.
  • In Tasmania, it has dramatically reduced juvenile native Tasmanian clam abundance in intertidal and shallow subtidal habitats.
  • It can damage commercial shellfish production and affect fisheries and aquaculture.
  • Its predation can indirectly affect shorebirds by reducing the availability of native prey.

How it spreads

  • Its planktonic larvae can drift long distances on coastal currents.
  • People can move crabs or larvae with fouled vessels, internal seawater systems, ballast water, aquaculture stock and equipment, or marine organisms and materials.
  • Movement of vessels and equipment from infested areas can spread crabs to new sites.

Control methods

  • Report suspected crabs, especially outside the known Australian range, promptly to the relevant state or territory biosecurity or fisheries agency and provide clear photographs or a specimen if requested.
  • Use surveys to establish the extent of an infestation; trained teams can use trapping and careful hand collection, with effort continued and adjusted based on follow-up monitoring.
  • Containment and movement controls may be needed to prevent crabs and larvae leaving an infested area; eradication is most feasible for small, enclosed or semi-enclosed infestations.
  • Clean or treat vessels, gear and aquaculture equipment only using methods approved by the relevant authorities, and prevent untreated material or water from returning to the marine environment.

Site hygiene and welfare

  • Before moving boats, ropes, traps or aquaculture equipment from an infested area, inspect and clean them, contain removed material, and follow local instructions for treatment and disposal.
  • Manage ballast water and other water from the area to prevent its discharge or transfer to uninfested waters.
  • Use methods set out in the national model codes of practice and standard operating procedures for the species.
  • Coordinate control with neighbours and the local government biosecurity plan, as isolated effort is quickly undone by reinvasion.

Classification by state

  • Australia (national): Priority marine pest. On the Australian Priority Marine Pest List, agreed by all governments as a marine pest of national concern.
  • Queensland: Prohibited matter. Report it to Biosecurity Queensland on 13 25 23 within 24 hours and do not move or deal with it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Notifiable aquatic pest. It must not be possessed, bought, sold, moved or released in NSW, and you must notify NSW DPIRD within one working day of finding it. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Noxious species. Declared a noxious species under the Fisheries Management Act 2007, so it must not be brought into South Australia, kept, sold or released, and it must not be returned to the water alive. Report any sighting to PIRSA FISHWATCH on 1800 065 522.
  • Western Australia: Noxious fish. Prescribed as a noxious fish under the Fish Resources Management Regulations 1995, so it must not be brought into WA, kept, sold or released. Report any sighting to FishWatch on 1800 815 507.
  • Tasmania: Declared pest. It is a declared pest under the Biosecurity Act 2019 (Tas). Report sightings to Biosecurity Tasmania and follow any management requirements.
  • Northern Territory: Not a declared pest. Not on an NT declared or prohibited list. Check with the NT Government before keeping, moving or releasing it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board

Sources