Researchers at the University of Exeter have found that the number of sea turtles along the coastlines of Ireland and the United Kingdom has declined in recent years. After analyzing records that dated back more than a century, the scientists were able to clearly confirm a recent drop in sea turtle sightings.
The team looked at records from 1910 to 2018 and found that citizen scientists and other witnesses had documented seeing nearly 2,000 sea turtles – some of which were stranded or captured.
The study showed that sightings increased dramatically in the 1980s and 1990s, which was likely due to an increase in the public’s interest in conservation, as well as improved methods of surveying and reporting. Since 2000, however, the population numbers have mysteriously dropped.
“Lots of factors could affect the changing of numbers of sea turtles sighted,” said study co-author Zara Botterell. “Climate change, prey availability and environmental disasters such as the 2010 Deepwater Horizon oil spill could all influence turtle numbers and behavior.”
“However, sea turtle populations in the North Atlantic are largely stable or increasing, and the apparent decrease may represent reduced reporting rather than fewer turtles in our seas. One reason for this could be that fewer fishing boats are at sea now than in the past – and fishers are the most likely people to see and report turtles.”
In Ireland and the UK, leatherbacks are the most common sea turtles. Leatherbacks made up 1,683 of the 1,997 sightings since 1910. They are thought to be the only sea turtle species that intentionally visits this region, arriving in summer in search of jellyfish.
Juvenile loggerheads and Kemp’s ridley turtles are usually spotted in winter, after they are likely carried in on currents and stranded.
Overall, there are seven species of sea turtles, and most are rare in the UK and Ireland. For example, from 1980 to 2016, only 11 green turtles, one olive ridley, and one hawksbill were spotted in the region.
The study was focused on information retrieved from the TURTLE database, which is operated by Marine Environmental Monitoring.
“We have been lucky to analyze this unique dataset that exists because Britain and Ireland are a real hotbed of engaged citizen science, where members of the public report their sightings in schemes supported by conservation charities and government bodies,” said study co-author Professor Brendan Godley.
The study is published in the Journal of the Marine Biological Association of the United Kingdom.