French oyster breeders introduced the Pacific oyster to the Bay of Biscay in the Atlantic to diversify the region's species and strengthen the commercial oyster industry, and with climate change warming Atlantic waters, the non-native oysters have spread up the coasts as far as Germany and Ireland, Inter Press Service reported Monday.
Unlike some invasive species, researchers say, the Pacific oyster plays well with other species.
On the German coast of the Wadden Sea the Pacific oysters, bigger than the native blue mussels, came to outnumber the native species.
However, "curiously, this invasion has not provoked any major harmful effects," biologist Christian Buschbaum of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven said.
"The local species accepted it. Although the oysters and mussels both feed on plankton, and now compete for it, the two species coexist well," Buschbaum said.
"The local mussel is a bit smaller than it was before the arrival of (the Pacific oysters), but, other than that, there have been no other negative impacts," he said.
In addition, the new arrivals brought with them a type of algae that has become a source of food for Haliichthys taeniophorus, a fish from the same family as seahorses, which for many years was considered threatened with extinction, Buschbaum said.