Danish oysters threatened by foreign invaders

The survival of Danish oysters is in question due to the spread of the invasive Pacific species, according to biologists. Hundreds of thousands of the foreign crustacean have taken over Danish waters after first being discovered off Jutland’s southwest coast in 1996. Since then, their numbers have increased dramatically and a particularly high concentration of the Pacific oysters found around Funen is causing concern for environmentalists.

The oysters have proven difficult to contain, which is bad news for the shellfish species that are indigenous to Danish waters. The blue mussel is one such order which is threatened, as the Pacific oysters out-compete them for food, which in turn threatens several bird species that feed on the mussels.

“We know that the oysters have reached Kerteminde Fjord and Odense Fjord,” biologist Tue Skovgard Larsen told Fyens Stiftstidende newspaper. “We also previously heard about it spreading to Horsens Fjord, so everything indicates that it’s quietly expanding southwards.”

“It’s estimated there are around 3,300 tonnes of Pacific oysters in the Wadden Sea alone right now,” Larsen added.

According to the Copenhagen Post, the oyster reefs grow quickly and attach themselves to mussel beds, spawning numerous larvae that can travel for miles. Many Pacific oysters also grow in clumps, making them difficult to open and less suitable for eating.

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