Study shows Risso's dolphins from same population

Risso's dolphins around the British Isles are part of a single population and are genetically distinct from those elsewhere in the Atlantic Ocean, new research shows.

Scientists studied the DNA of stranded dolphins in England, Scotland and Wales from1992 to 2016 and said there were "no significant genetic differences" between the animals.

The dolphins have tall dorsal fins and distinctive scarring on their grey bodies and more sightings have been recorded off Cornwall, attracted by food, it is thought.

Nicola Hodgins, from marine charity Mara and a visiting fellow at the University of Exeter, said skin and tissue samples from the dolphins provided "an amazing amount of information".

Hodgins told BBC Cornwall there was evidence that particular dolphins were returning to the same place year after year and they could be identified from a photographic catalogue researchers had been building up.

She said: "This means, if anything happens to these dolphins, if their populations really start to decline, they are not going to be replaced.

"There's not going to be immigration of dolphins from elsewhere, so we really do have this isolated population.

"We need to be looking at more site specific management issues just because they're all related."

She said the increase in sightings of Risso's off Cornwall were likely to be driven by the "increase in food availability".

"It would make perfect sense that with an increase in food availability that's where they're tuning up."

It is thought increases in the numbers of octopus off Cornwall and Devon because of the warmer sea temperatures are among the factors which have attracted the dolphins.

Hodgins added more people were also looking out them too, which was also likely to increase the numbers recorded.

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