Oyster ‘invasion’ a blessing and curse

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Much like the fishing industry’s initial despair over the arrival of king crab in Norwegian waters, marine researchers aren’t particularly pleased with the arrival of another “invading” species along the coast: oysters originally from the northern Pacific. First spotted more than 30 years ago, they’ve begun congregating along the southern coast from Hvaler over to Kristiansand, and north along the West Coast.

A new breed of oyster is "invading" the Norwegian coast, posing both problems and commercial potential. PHOTO: Havforskningsinstituttet/Espen Bierud

A new breed of oyster is “invading” the Norwegian coast, posing both problems and commercial potential. PHOTO: Havforskningsinstituttet/Espen Bierud

“The oysters are one of the extreme examples of so-called invading species,” Stein Mortensen, senior researcher at Norway’s Institute of Marine Research, told newspaper Bergens Tidende. “We see that the ecosystem changes where they establish themselves.”

He said history is repeating itself: “First there’s a period where we see just a few shells, and everyone thinks they won’t expand because of low temperatures and other conditions, but then they adapt and we get periods of high temperatures. The development can be explosive.”

It’s arguably approaching that level now in Norway, with researchers fearing the sharp-shelled oysters will ruin swimming areas and challenge other species. Others see the oysters as a potentially valuable new source of food, since oysters, like the king crab that’s become a lucrative export product, can be a delicacy fetching high prices.

Mortensen warned they can also be poisonous, however, like the mussels that also flourish along the Norwegian coast. “Especially in the winter there can be a danger of virus in the shells that can case stomach upset,” he said. “We generally advise that oysters we harvest ourselves should be cooked before eaten, otherwise there’s a risk in eating them.”

It’s not entirely clear how they migrated from the Pacific to the North Atlantic and further into the North Sea. Some point to commercial farming of the species, known as giga oysters, off the coast of Northern Europe that spread on its own. Mortensen said the research institute (Havforskningsinstituttet, based in Bergen) is now working on a Scandinavian cooperation project to monitor how the oyster population is growing and how they could be commercially harvested.

newsinenglish.no/Nina Berglund