Conservation efforts may have boosted the number of marine turtles visiting waters off the coast of Cornwall. A study by biologists from the University of Exeter's Tremough Campus, Penryn, analyses 100 years of data and shows an increase in turtle sightings in UK waters, including off the Cornish coast.

The research by the University of Exeter and Marine Environmental Monitoring, which is published this week in Marine Biology shows an increase in the number of loggerhead and Kemp's ridley turtles in UK and French waters in the last twenty years. The research team believes this is most likely the result of protective measures put in place in the United States and Mexico.

Almost half of all sea turtle sightings in UK waters were off the coast of Cornwall, which has a recorded 225 sightings in the last 100 years. Across the south west peninsula, 333 turtle sightings were recorded over the last century. The most frequently sighted turtle species are leatherbacks, which are mainly seen in the summer, though during the winter hard-shelled species including Kemp's ridley turtles and loggerheads are seen. Sightings of all species have gradually increased over the last century decade on decade.

"The data tells the story of the interaction between marine turtles and humans over the last hundred years," said Matthew Witt of the University. "Following a severe decline as a result of human activity in the first-half of the last century, we can now see the positive effect that recent conservation efforts have had on these turtle species."

A large majority of marine turtles that visit Northern European waters hatch in the Americas and can spend nearly four years travelling thousands of miles to British waters. Scientists do not know why some juvenile turtles make the journey to Northern Europe, but believe they may simply be driven by the North Atlantic current system.

The eggs of Kemp's ridley turtles were harvested in huge numbers and the species reached near-extinction before protective measures began in the mid-1960s. Absent from UK records since 1974, sightings of this species returned in the 1990s, which coincides with the increasing use of turtle excluder devices in shrimp nets in US and Mexican waters. Both species occurred in western parts of the UK and France, including a number of sightings off the coasts of Devon and Cornwall.

The decline of sea turtles has led to a global protection effort. Measures have included the introduction of turtle excluder devices in fishing nets and hatcheries to protect eggs.

Matthew Witt concludes: "The increase of turtles in the sea off the south west coastline could be indicative of a global trend. Though numbers are increasing, it is still incredibly rare and special to see a marine turtle."