image downloaded from Naturdata
Chinese Mitten Crab (Eriocheir sinensis, H. Milne-Edwards, 1853)
Origin: East Asia (from Korea to China)
Size: 5 to 7 cm (size of the carapace), maximum 10 cm
The Chinese Mitten Crab is a medium size crab, has square shaped carapace (distinguished from other European species) and hair-like covering on the fore claws (well developed in males). The colour varies from brownish to yellow on the upper side and whitish underneath. The juveniles are very small; after reaching a size of 2 cm, it is possible to distinguish males from females by the shape of the abdomen, which is rounded in the female and occupies most of the area of the thorax and narrow and shaped like an inverted funnel in males.
image downloaded from Wilder
This species spends most part of its life in fresh or brackish water and can tolerate wide variations of salinity. The adults migrate downstream, in fall, to reproduce in salt or brackish waters. Females carry the eggs and after hatching, larvae are planktonic for 1 or 2 months. During this marine free-swimming phase, larvae pass through a series of development stages. At the end of summer larvae metamorphosis into juvenile crabs that settle in the bottom and migrate upstream to fresh water.
The Chinese Mitten Crab is omnivorous and opportunistic, feeds on a wide variety of food, according to the food availability: plant matter, invertebrates, fish and molluscs (sea shells). This species moves from fresh water habitats (juveniles) to salt water habitats in order to reproduce; occupies different ecosystems according to its life stage (estuaries, bays and rivers).
The pathway of invasion, probably was in water tanks of commercial ships. This species was first recorded in Europe in 1912, in Germany and in 1992 arrived to USA and in 1999 was already in Western Europe. In Portugal it is present in Tagus and Minho River. According to the IUCN (International Union for the Conservation of Nature) is among the 100 worst invasive species of the world, because it causes a negative impact in the ecosystems, completion with native species and reduction in biodiversity.