The Global Spread of the Chinese Mitten Crab Eriocheir sinensis
Bella S. Galil, Paul F. Clark, James T. Carlton
Chinese mitten crabs are one of the World’s most notorious aquatic invasive species. Their catadromous life history, in which they spend most of their lives growing to maturity in freshwater, and their extreme euryhalinity, has made it relatively easy for the species to gain a foothold in the World’s river systems. Ballast water introductions are thought to have brought them to continental Europe in the early twentieth century. These will have probably been as larvae, which will then have settled in the estuaries subsequently moving upstream as juveniles. The capacity of these crabs to move upstream (and over land) is staggering and indi- viduals in their native range in the Far East have been found more than 1,000 km from the sea, where they must return to breed. A number of successful separate introductions of mitten crabs have taken place in Europe, including the UK and America. Europe (Northern Germany) saw initial introductions in 1912, followed by others into both the North Sea coasts and English Channel coasts of France. The extensive network of Northern European waterways facilitated the spread in river systems. After a lag phase, which is typical of many invasive species following introduction, numbers of mitten crabs increased dramatically such that by 1936 attempts at removing the animals from rivers in Germany were abandoned; some 220 metric tonnes were removed from the River Weser alone in that year. Introductions into the UK (River Thames) followed in the mid-1930s but initial introductions appear not to have founded a population. It was not until 1970s that mitten crabs numbers increased and the Thames population became established, and it has subsequently increased and spread. The crab had spread rapidly both around UK coasts and up river systems by the end of the twentieth century and into the 1st decade of the 21st. Evidence suggests that there have been several separate introductions in France; the first in Northern France and then subsequently into western France.