The species that has now been discovered is a marl crayfish, with the Latin name Pontogammarus robustoides. It was found at the end of September near Kungsängen in Upplands-Bro.
The crustacean, which grows to about one to two centimeters, is seen as a threat to native species.
– It is a small predator that eats up the food for the native marl crayfish. It lives close to the shore in lakes and larger watercourses, so it also affects many other small animals that are there, says Carin Nilsson, group manager and expert in freshwater at the consulting company Sweco, which made the find.
Originally, the species comes from the area around the Black Sea and the Caspian Sea. It has previously been found in Lithuania, Poland and Germany, among others.
– The most likely thing is that it has been transported here with water, perhaps with ballast water, says Carin Nilsson.
The Swedish University of Agriculture has a list of eight species of invasive marl crabs where the risk is assessed to be high for them establishing themselves in Swedish waters. The latest find is the third of the species found in Sweden in the past year.
At the beginning of March, the Norwegian Sea and Water Authority confirmed that the species greater predatory merle had been found in Vättern’s shore zone. A few weeks later, a find of another species of marl crayfish was found in Lake Tulingesjön in Botkyrka.