The American lobster is considered an alien species in Swedish waters. Its presence can introduce new and very serious diseases and parasites that affect both our domestic European lobster and other shellfish. The Swedish Agency for Marine and Water Management supports the efforts to stop the import of living American lobsters.
American Lobster a Threat Against to Native Species
It is illegal to release American lobsters into Swedish waters. Because the selling of live specimens is made directly to the general public, it is impossible to monitor the ban.
How the American Lobster Spreads in Sweden
The American lobster can either be deliberately released or escape from its storage cage in the water. Specimens that are caught in Norwegian and Swedish waters sometimes still have the North American exporter's rubber bands around their claws. A natural immigration from North America is an entirely excluded option.
The American lobster can be found at the same depths as its European counterpart, down to about 50 meters, but it can also subsist over 200 meters below the surface. At such depths, it can escape fishing pots and grow its population. If this occurs, the species' introduction into Swedish waters is unavoidable. Acting quickly to its discovery is therefore important.
Diseases and Parasites
The North American lobster fishery has locally been severely affected by the outbreak of diseases. Strains with a high mortality rate, such as the bacterial disease Gaffkaemia, occur in tanks where lobsters have been stored for export.
In the ocean, the epizootic shell disease is complex and causes major defects on the lobster's shell. This in turn makes them unmarketable and can mean great loses for the fishing industry. The disease can even lead to the specimen's death.
The species carries many other diseases but the scientific knowledge behind them is still low. They carry parasites that can cause harm, for example by eating up the lobster's eggs. Such parasites can even spread to crabs. As of present, these parasites have not been found in Swedish waters.
A Direct Effect to the European Lobster
It is still fully unknown as to how the American and European lobsters affect each other. A female American lobster in the wild was found to have been fertilized by a male European specimen in Norwegian waters, and American lobsters with the epizootic shell disease have been discovered in the Norwegian area of the Skagerrak.