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Tuesday, September 27, 2011

Dolphins vanishing from the Cornish coast thanks to pollution and over-fishing

By Tamara Cohen

They were once a common sight along the Cornish coast, where their acrobatic feats have delighted visitors for decades.

But the county’s bottlenose dolphins could soon be no more than a memory, experts have warned.

Their numbers have plummeted from around 20 in 1991 to just six today, as they fall victim to fishing nets and pollution.

Rare sight: The number of bottlenose dolphins found off the Cornish coast has dwindled from 20 in 1991 to just six today

According to the Cornwall Wildlife Trust, 20 years ago the playful creatures accounted for 67 per cent of all marine animal sightings, but by 2008 that figure had fallen to 27 per cent.

Ruth Williams, the Trust’s marine conservation manager, said: ‘The group size is now extremely low and we are concerned for their future. Although young dolphins are seen each year, the reported group size does not seem to be growing.

‘If they were to vanish from Cornwall, it would be a severe blow for the marine environment and terribly sad for the many people who come to see these magnificent creatures. They do come very close to the shore here and are a very special sight.’

Since 2008 their numbers have remained static at between six and eight, with just one or two young dolphins spotted in the group – far fewer than in the past.

Conservationists do not fully understand the reasons for their decline, but believe some may have been poisoned by chemicals in the sea.

Miss Williams added: ‘The reasons are not clear and it’s really a jigsaw puzzle but recent post-mortems suggest they have ingested chemicals called polychlorinated biphenols (PCBS) which are found in all sorts of flame retardant materials.

‘Because Cornwall has a small population of bottlenose dolphins, losing a few individuals can make a massive difference, whereas larger groups may be more resilient.’

Cornwall prides itself on its regular community of bottlenose dolphins which come right up to the seashore almost every day in the summer months.

There are two other sites where bottlenose dolphins are seen in the UK – Cardigan Bay in Wales and Moray Firth in Scotland which have much larger populations of more than 100.

The Trust have been researching their numbers in collaboration with Exeter University researcher Stephen Pikesley, who has written an academic paper on their decline which will be published in the Journal of the Marine Biological Association of the United Kingdom next month.

He said: ‘When we analysed these data it was clear that there were significant decreases in the number of bottlenose dolphin sightings between 1991 and 2008. We also found that the size of bottlenose dolphin groups had decreased.’



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