The european or green shore crab

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.

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.

In NSW there are historical sightings of the crabs in Jervis Bay, Lake Conjola, Burrill Lake, Narrawallee Inlet and the Sydney area. In recent years green shore crabs have been documented by NSW DPI in eleven estuaries on the NSW south coast: Wonboyn Lake, Twofold Bay, Pambula Lake, Merimbula Lake, Nelson Lagoon, Wapengo Lake, Cuttagee Lake, Bermagui River, Nangudga Lake, Wagonga Inlet and the Clyde River.

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

Impacts

The European green crab has been documented to have effects on native species and aquaculture industries overseas where it competes with native species. 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 the aquaculture industry if populations become large. Some NSW oyster farmers have reported observing oyster mortalities from crabs locally, although these mortalities have not been confirmed to be from European green crabs, while 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 by the shipping industry in ballast water. Ballast water, biofouling of coastal vessels and accidental transportation in oyster trays and baskets are all potential dispersal mechanisms for the European green crab.

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. I&I NSW  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 on the European green crab and an identification card to assist in identifying this pest species from similar native species.
I&I NSW is asking oyster and mussel farmers to report detailed information including the type of cultivation crabs are found in and any impacts on production.

Similar native species

Thalamita sima

Key Features:

• Green / yellow colour
• 5 spines on either side of eyes
• swimming paddles
  

Ocean surf crab / Sand crab Ovalipes australiensis

Key Features:

• Grey / sand colour
• 5 spines on either side of eyes
• swimming paddles
• 2 dark spots on rear

Rough rock crab / Red swimmer crab Nectocarcinus integrifrons

Key features:

• Red / brown colour
• 3 spines on either side of eyes
• No swimming paddles
• Ends of claws are black
  

How can you help?

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

Report any suspected new sightings to I&I NSW on the 24 hour recorded hotline: 02 4916 3877 or email aquatic.pests@industry.nsw.gov.au.

If you are unsure of the species please take a photo or collect a sample (freeze crab in plastic bag) and send to I&I NSW Aquatic Biosecurity Unit, including a description of where it was found and GPS points or a map if possible.

If you see this pest in NSW, please report it immediately

• Note the exact location
• If possible take a photo and/or collect a sample
• Freeze sample in a plastic bag
• Report your sighting

For further information

• (www.marine.csiro.au)

Photograph credits

Native species: Graham Edgar, Australian Marine Life. European green crab: Pat Tully.