Description
This crab is also also commonly known as the European shore crab. C. maenas can live in all types of protected and semi-protected marine and estuarine habitats, including habitats with mud, sand, or rock substrates, submerged aquatic vegetation, and emergent marsh, although soft bottoms are preferred. It can withstand wide ranges of salinity and temperatures.
Where did they come from?
It is native to European Atlantic waters and the Baltic Sea, with temperatures of between -2 and 12oC. It has colonised habitats in Australia, South Africa, South America and both Atlantic and Pacific coasts of North America.
Where are they found in Australia?
In Australia, C. maenas was first reported in Port Phillip Bay, Victoria in 1902. It has since spread along the south-eastern and south-western seaboards, reaching New South Wales in 1971, South Australia in 1976 and Tasmania in 1993 and has also been found in Western Australia.
How was it introduced?
C. maenas has the ability to disperse by a variety of mechanisms, including ballast water, ships' hulls, packing materials (seaweeds) used to ship live marine organisms, bivalves moved for aquaculture, rafting, migration of crab larvae on ocean currents, and the movement of submerged aquatic vegetation for coastal zone management initiatives. The Green crab most likely found its way to Victoria during the 1850s, when old lumber ships visited Port Phillip Bay to unload passengers heading for the gold fields.
What is its impact?
It is a large, active predatory crab that matures at two to three years of age, breeds up to three times within a year and lives up to five years. A female Green crab may carry up to 200,000 fertilised eggs. underneath their abdomen. They grow quickly and can grow to reach about 9 cm in width,
They feedi mostly on plants and soft-shelled animals when small ( less than3 cm) and hard-shelled animals, such as crustaceans, molluscs and polychaetes, as they grow larger. In Australia they may have a great impact including direct impacts on prey species, indirect effects on species competing for the same prey, and indirect impacts on nutrient availability (by removing bivalves which filter algae and larvae).
How is it controlled?
Currently, the only control measure implemented for green crabs is their physical removal. Traps are used, yielding catches of up to 430 crabs per trap. In Australia it is preyed on by larger species of crab.
In Massachusetts (USA) , a bounty was levied in 1995 for catching C. maenas, to protect local shellfish, and 10 tons were caught. |
