This is the third time this type of crustacean, colloquially called the Japanese shore crab or Asian shore crab, has been found in Swedish waters since 2012, reports news agency TT.
Researchers are worried that these crabs will drive out the native species.
Dr. Matz Berggren, a researcher at the Department of Marine Sciences at Gothenburg University, says he's not happy about hearing the report, and that it indicates that the problem still exists. He fears that more such crabs are going to turn up.
A child found this latest specimen while hunting for crabs at Hönö, in Gothenburg's northern archipelago. The first time one of these crabs turned up in Sweden, it was also discovered in the same area. The second one however, which was found last year, was found in the area near Ringhals, south of Gothenburg.
Berggren believes the crabs came in with ballast water from some kind of boat. He believes it's highly unlikely that only three of these crabs have arrived, and that all of them have been reported.