The European green crab (also known as European shore crab or green shore crab).
Image: Pat Tully

Identification

The European green crab, also known as the European shore crab or green shore crab, is a medium sized crab with three blunt spines between the eyes (rostrum) and five pointed spines either side of the eyes. The adult crab ranges in colour from an olive to dark green, often with yellow or orange patches underneath while juveniles can be a lighter pale sandy colour. They have a broad triangular shaped shell usually 5 to 6 cm in width but have been known to reach 9cm. They do not have flattened swimming flippers.

Juvenile European green crab.
Photograph: Matt Tyler

Similar native species

These native species may be confused with this marine pest.

Photo: Graham Edgar, Australian Marine Life

Photo: Graham Edgar, Australian Marine Life

Photo: Leon Altoff

Distribution and habitat

The European green crab is native to the Atlantic Coast of Europe and northern Africa. However, the crab has spread to other countries including North America, Japan, South Africa and Australia. Records indicate that this crab was first documented in Australia in 1900 in Port Phillip Bay. It has been found in Tasmania, Victoria, South Australia, Western Australia and New South Wales, where there are historical records from the Australian Museum of sightings in several south coast and Sydney estuaries.

In NSW there have been recent sightings of the crabs in Clyde River / Batemans Bay, Tomaga River, Candlagan Creek, Coila Lake, Lake Mummuga, Wagonga Inlet, Nangudga Lake, Corunna Lake, Tilba Tilba Lake, Wallaga Lake, Bermagui River, Cuttagee Lake, Wapengo Lake, Nelson Lagoon, Merimbula Lake, Pambula Lake, Twofold Bay (including Curalo Lagoon, Shadracks Creek, Nullica River, Towamba River / Kiah Inlet, Fisheries Creek), Wonboyn Lake and Nadgee Lake.

The European green crab can live in a variety of habitats but is most often seen close to the shore on mudflats or amongst rocks in protected marine bays and estuaries.

Impacts

The European green crab has been documented to have effects on native species and aquaculture industries overseas. It is a voracious predator that feeds on many types of organisms including shellfish and other crabs. The European green crab has the potential to impact shellfish aquaculture industries if populations become large. Some NSW oyster farmers have reported observing oyster mortalities possibly due to predation by crabs, although these mortalities have not been confirmed to be from European green crabs.  Other farmers have not observed any impacts on production.

There is no current evidence in NSW that the crabs are affecting biodiversity.

How did they get here?

The European green crab is thought to have been originally introduced to Victoria in the late 1800s in the dry ballast of wooden ships. Much of its subsequent spread has probably been by natural dispersal in oceanic currents, but it may have also been spread by boats and ships and accidental transportation in oyster trays and baskets.

What is being done?

In August 2009, the Minister made an emergency declaration to list the species as a Class 1 Noxious fish under Section 209 of the Fisheries Management Act 1994. This declaration prohibits the possession and sale of live European green crabs. 

Eradication of any pest, including the European green crab is very difficult once the species becomes established. NSW DPI is endeavouring to gain a better understanding of the distribution, abundance and potential impacts of the European green crab through ongoing surveillance to trap for this crab throughout several NSW estuaries and coastal lakes.

All oyster and mussel farmers have received information including a NSW DPI pest identification card for  the European green crab to assist in identifying this pest species from similar native species. Where oyster and mussel farmers report seeing this pest species on their infrastructure, NSW DPI is asking them to provide details of the type of cultivation the crabs are observed on and any impacts they may be having upon production.

NSW DPI  is continuing to  support the efforts of local groups to reduce the number of crabs in limited areas, most particularly the European green crab trapping program being undertaken (with Commonwealth grant funding and the assistance of volunteers) by the Sapphire Coast Marine Discovery Centre at Eden and the Southern Rivers Catchment Management Authority. This project is also raising community awareness of the crab and working with oyster farmers to determine if different types of oyster infrastructure are more effective in reducing crab presence.

NSW DPI is also collaborating with researchers at Macquarie University and Batemans Marine Park (in partnership with Southern Rivers Catchment Management Authority and the Sapphire Coast Marine Discovery Centre) who are investigating the biology and ecology of European green crabs in coastal lakes of southern NSW.

How you can help

Learn to recognise, and be aware of, the European green crab so that you can report any suspected new sighting to NSW DPI Aquatic Biosecurity.

Click here to report any suspected new sightings or call the 24 hour recorded hotline: 02 4916 3877 or email aquatic.pests@industry.nsw.gov.au.

Please take photos or collect a sample (freeze crab in plastic bag) and contact NSW DPI Aquatic Biosecurity, including a description of where it was found and GPS points or a map if possible.