First-ever Migratory Freshwater Crab in the St. Lawrence River
|Chinese Mitten Crab (Eriocheir sinensis)|
A Surprising Discovery in the Water of the St. Lawrence River
While conducting sampling activities in the Quebec City area, Yves de Lafontaine, a research scientist at the St. Lawrence Centre, was approached by a fisherman about an unusual catch hed made on September 2, 2004. The strange-looking crab was caught in an eel trap near Lévis (Saint-Romuald), on the south shore of the St. Lawrence River, just opposite Quebec City.
The live specimen was identified as a Chinese Mitten Crab (Eriocheir sinensis), so called for its hairy claws that resemble paws. According to experts at the St. Lawrence Centre and the Parc Aquarium du Québec, this is a female of approximately one and a half years old, weighing 40 g and with a carapace of 4.6 cm wide. The species is considered one of the 100 most invasive species on the planet.
This is the first sighting of this exotic species in the waters of the St. Lawrence River, although a few individuals were found in the Great Lakes in the 1970s.
The Chinese Mitten Crab is catadromous and therefore requires both fresh and salt water to complete its life cycle and ensure the establishment and maintenance of the population. Adult crabs migrate from fresh water to salt water to reproduce. Following the larval period, juvenile crabs migrate to fresh water, where they grow and mature. The species migrates over distances of up to 500 km in the rivers of Europe and Asia.
The Chinese Mitten Crab is a native of the rivers and estuaries of the Yellow Sea, between China and Korea. It was introduced by accident in Germany in 1912 and has spread to many European countries and, most recently to England. It established itself in San Francisco Bay on the U.S. west coast in 1992. In Canada, its presence was noted for the first time in 1965 in the Detroit River in Windsor, Ontario, then in Lake Erie in 1973.
In the Great Lakes, this species is thought to be incapable of establishing itself on a long-term basis because of its catadromous nature. Its presence in the water near Quebec City, however, entails a risk of the population establishing itself in the St. Lawrence River and its estuary. Due to the very invasive nature of this species, the tributaries of the St. Lawrence River and Estuary, including the Saguenay River, are also perceived as areas at risk.
The species burrows into riverbanks, leading to their erosion and collapse. They are also known to block the water intakes in irrigation canals.
Hmmmmm. They block intakes. Then power plant operators can get freshly cooked crab for midnight meals by just goign to the outlet water boxes of the condensers!