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Endangered pearl mussels that live 200-plus years may be making comeback

The populations of freshwater pearl mussels have been declining in Ostrobothnia and some of them may have witnessed the decline themselves over the centuries. The endangered species – which can live up to 250 years of age – may see a resurgence thanks to measures taken by local environmental researchers.

Jokihelmisimpukka kädessä.
Freshwater pearl mussel. Image: Kalle Niskala / Yle

The endangered freshwater pearl mussel may be experiencing a revival in the Ähtävänjoki river in Ostrobothnia.

Last autumn, after a steady decades-long decline in the river's mussel population, one of Finland's Centres for Economic Development, Transport and the Environment (called ELY centres) moved the creatures upstream to a more fitting location.

ELY centre researcher Eero Mäenpää says the move has had positive results.

"The mussels seem to have survived the winter well, we haven't found any dead specimens," he says. "I was actually surprised by their great condition."

By autumn the data will be in on whether the freshwater pearl mussels have been able to breed new larvae which could then be moved to a Norwegian breeding establishment. Once the molluscs develop enough there, they can then be reintroduced into the Ahtävänjoki river.

"Chances of success are high if this summer turns out to be regular enough. We've tried to save these mussels for two years, and we're running out of time," says Mäenpää.

"Now or never"

Conditions in Ähtävänjoki are dire: solid effluents and high acidity levels have been killing the rare freshwater pearl mussels (Margaritifera margaritifera) for decades. Just five years ago thousands of molluscs lived in the river, while now the local population is counted in the hundreds. In the early 1980s, Mäenpää says, Ähtävänjoki was home to as many as 50,000 mussels.

"The rate of disappearance has been very fast. It's now or never if we want to save the Ähtävänjoki mussels, because they will vanish if we don't intervene – and even then nothing is certain," Mäenpää says.

However, the University of Jyväskylä has more good news: 150 mussels were moved to the Konnevesi research facility last autumn, and are doing well.

"We've only found three dead mussels, which is surprisingly few. And the rest are getting along fine."

The Ähtävänjoki river is part of the European Commission's LIFE project, which directs funds towards environmental protection initiatives – including saving the freshwater pearl mussel, which can have a lifespan of more than 200 years.

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