Beach walkers urged to report any sightings of 'invasive' blue crab

Beach walkers urged to report any sightings of 'invasive' blue crab

The first blue crab sighting in Ireland on February 15, 2021, on Dollymount Strand. Picture: Ruth McManus / National Biodiversity Data Centre

It may be a pleasantly exotic surprise when roaming the beach, but the public has been told that any sightings of blue crabs should be reported to biodiversity experts as soon as possible.

The National Biodiversity Data Centre, the organisation which collects and analyses data on Ireland’s biological diversity, warned that the first official blue crab sighting on the country's shores could be a sign that they have entered the Irish ecosystem, potentially threatening the existing environment.

It said there was currently limited information on the occurrence of this species in Ireland, hence the call for people to submit any suspected sightings with photos.

"This is the first blue crab sighting in Ireland, and it was seen and photographed on February 15 by Ruth McManus on Dollymount Strand," the centre said.

"A second report was submitted on March 9 by Wesley Bell, this time of a blue crab claw found on Dollymount Strand."

It is suspected that this crab claw may have come from the blue crab seen on February 15 that was left on the strand.

According to Invasive Species Ireland (ISI), creatures not native to ecosystems are the second greatest threat to biodiversity worldwide, after habitat destruction. 

Invasive species can negatively impact on native species, transforming habitats and threatening whole ecosystems, causing serious problems to the environment and the economy, ISI said.

Since the 17th century, invasive species have contributed to nearly 40% of all animal extinctions for which the cause is known, according to the ISI.

Annual environmental losses caused by introduced pests in the US, UK, Australia, South Africa, India, and Brazil have been calculated at over $100bn (€85.5bn), it added.

The National Biodiversity Data Centre said it is unknown how the blue crab came to be at the beach, but investigations by authorities are ongoing.

"It may have been a been purchased live — possibly from food trade — and intentionally released, but died," the centre said.

"It may have been unintentionally transported here in ship ballast water or on a ship's hull. It may have naturally spread from other areas it has become established such as some coastal areas of Portugal, Spain and France."

There have been few records of blue crabs from other European countries such as Denmark, Netherlands, Germany, and Norway, but none before for Ireland or the UK, according to the centre.

The blue crab is native to the Atlantic coast of the US, but has now established itself in Mediterranean coastlines as an invasive species.

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