Invasive predator shrimp species discovered in Rauma port

A new invasive species threatening native aquatic life has been found in the port of Rauma, according to the Finnish Environment Institute (Syke).

The predator shrimp (Palaemon elegans), first detected in a 2024 sample, poses a significant risk to brackish and freshwater invertebrates by outcompeting and displacing native species. The aggressive invader grows up to 2–3 cm in length—larger than Finland’s native shrimp species—and reduces biodiversity through efficient predation and competition.

“For a shrimp species, it’s quite large,” Syke researcher Okko Outinen told STT. So far, the predator shrimp has only been found in Rauma port.

The species spread to European coastal waters in the 1990s and later to inland waters this century. Nearby populations exist along the coasts of Latvia, Lithuania, Poland, and Germany, as well as in lakes in Sweden and Denmark.

Invasive species surge in Finnish waters

Over the past 30 years, 20 new non-native species—more than half of all recorded marine and coastal invaders in Finland—have arrived in Finnish waters, often via ships and recreational boats. Enhanced port monitoring since 2020 has accelerated discoveries, with most new species being small invertebrates like molluscs, polychaete worms, and crustaceans living in sediment or shoreline vegetation.

Public reports also aid detection. Observations can be submitted via the vieraslajit.fi website, which provides identification guides and images of invasive species.