Action to prevent thousands of turtles being trapped by abandoned fishing nets in the Indian Ocean is needed urgently, a University of Derby study has concluded.

Researchers are recommending that manufacturers and fishing authorities improve the traceability of nets and other fishing gear to reduce turtle deaths caused by the so-called “ghost nets”, which break off or are discarded.

The study, published under the title ‘Untangling the origin of ghost gear within the Maldivian archipelago and its impact on olive ridley (Lepidochelys olivacea) populations’ in the open access journal Endangered Species Research, examined information about “ghost nets” found around the Maldives in the Indian Ocean over a period of 51 months.

The information was collated by the UK-based Olive Ridley Project charity, which was set up by University of Derby researcher Martin Stelfox in response to the large number of Olive Ridley sea turtles he found entangled in nets while on research trips to the Indian Ocean.

Over that time period, a total of 752 abandoned nets were found and 131 turtles entangled in netting. Around 97 per cent of the turtles found entangled were Olive Ridley turtles.

However, it has been estimated that this number of “ghost nets” could actually have entangled between 3,400 and 12,200 turtles in that time.

The study found that nets with a larger mesh size, nets which were blue in colour, and fragments of net which did not have floats attached to them were more likely to cause entanglement.

Martin said: “What this research gives us is an opportunity to look at the feasibility of making fishing gear, including nets, more traceable to the individuals, companies and communities using it.

“That will require better co-ordination and information-sharing between manufacturers and the authorities which regulate sea fishing around the world.”

One possible solution is to use blockchain data storage technology, which is already being trialled in the Pacific, to improve traceability and accountability in the fishing industry.

The impact of seasonality, particularly the north-east monsoons, and the migration patterns of Olive Ridley turtles to identify where they overlap with fishing activity, should also be the subject of urgent future research, the study advocates.

The report states: “Temporary closures in these overlapping areas during high turtle activity may reduce the likelihood of turtle entanglement as a result of gear loss caused by operational damage or general discard.

“Moreover, establishing free, port side or landing site recycling facilities would discourage small and large-scale fishers from dumping damaged or end of life gear at sea.”

Martin said: “While our solutions must be realistic and workable, they could, if implemented, reduce the amount of fishing equipment which is lost in the ocean and could help encourage better reporting of gear which is lost.

“That could, in turn, lead to fewer turtles dying after becoming entangled in ghost nets in the ocean.”

Every year, it is estimated that 640,000 tonnes of ghost nets are discarded at sea, which amounts to 10 per cent of the world’s total marine debris. Ghost nets are commercial fishing nets that have been lost, abandoned, or discarded at sea.

Every year, they are responsible for trapping and killing millions of marine animals including sharks, rays, bony fish, turtles, dolphins, whales, crustaceans, and birds. Ghost nets cause further damage by entangling live coral, smothering reefs and introducing parasites and invasive species into reef environments.

Between July 2013 and July 2018, there were 601 turtle entanglements recorded in discarded fishing nets in the Maldives alone.

The Maldives is home to five species of sea turtles, the most frequently spotted out of these five are the Green Sea Turtle (Chelonia mydas) and the Hawksbill Turtle (Eretmochelys imbricata). Loggerheads, Leatherbacks and Olive Ridley turtles are the rarer species. Although all species of turtles have been protected by law in the Maldives since 1995, the major threats to these animals continue to be egg and meat poaching and entanglement in marine debris.

All seven of the world’s species of sea turtles are on IUCN’s Red List with the Hawksbill turtle being listed as the most critically endangered out of the seven.