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Sightings of sea turtles around the coasts of the UK and Ireland are showing signs of decline, scientists say, although it is unclear what is behind the drop.

Studies show that between 1910 and 2018 there were 1,997 recorded sightings of turtles - with 84% of these being leatherback turtles.

However, the team behind the study say the records show a downward trend.

They say reports of leatherback turtles reached a peak in the 1990s, but since then records appear to have gradually declined.

It has gone from 553 sightings in the 1990s, to 464 in the 2000s, and just 256 since 2010 - although the data for the most recent decade is not yet complete.

Zara Botterell, lead author of the study from the University of Exeter, said the apparent decline could be down to many different factors:

"It could be climate change, or prey availability, but it could also be reporting," she said, noting there has been a decrease in the number of fishing boats operating in the UK - a key source for turtle sightings.

Leatherback sea turtles can be spotted around the UK and Ireland, but they originally come South Africa and the Caribbean.

That's a long way from the UK, but they don't just swim here for the fun of it! One of the reasons they swim to the UK is to eat our jellyfish.

They get their name because they don't have a hardback shell like other sea turtles, instead, they have thick leathery skin, hence the name!

The study, which was published in the Journal of the Marine Biological Association of the United Kingdom, also revealed findings on other types of turtles.

Records of Kemp's ridley turtles have increased since the 1980s, although they have also now seen a recent decline - but only in the past couple of years.

Other turtle sightings recorded included green turtles, and an olive ridley turtle, a small species that favours tropical waters, but one was stranded on Anglesey in Wales, in 2016.

While leatherback turtles come to UK waters looking for jellyfish, loggerheads and Kemp's ridley turtles are transported into the area on currents from the Caribbean or North Atlantic.