Satellite tracking of olive ridley sea turtles off the coast of Central Africa has revealed that existing protected areas may be inadequate to safeguard turtles from fishing nets, according to scientists.

A nesting olive ridley sea turtle on the coast of Gabon. [Wildlife Conservation Society]

The research team, made up of experts from the Wildlife Conservation Society, the University of California-Santa Cruz and the University of Exeter, are now recommending the extension of an international marine park that spans the waters of Gabon and the Republic of Congo and better global cooperation to manage this threatened species.

First author Sara Maxwell said it provides novel insights into the movements of olive ridleys and how to better protect them. 'Thousands of olive ridley sea turtles are caught every year in fishing nets along the coast of Central Africa, yet we previously had no understanding of their movements or what areas are critical to protect their populations,' said Maxwell, who now works for the Marine Conservation Institute.

Tracked the progress of 18 females In the first comprehensive tracking study of olive ridley sea turtles during the nesting season, the authors used satellite transmitters to follow 18 female turtles as they came ashore to lay eggs. The nesting season brings the turtles closest to the coastline and to the danger of being captured in fishing nets.

Turtles were tagged in Mayumba National Park, a 900sq km marine protected area on the southern coast of Gabon. Mayumba National Park and Conkouati-Douli National Park just across the border in the Republic of Congo were created to protect both olive ridley and leatherback sea turtles from fishing nets, but dozens of dead continue to wash up on the shores of the park.

These deaths have perplexed park managers and resulted in mounting concern about the health of this threatened species. 'What we found, however, made sense. Turtles were regularly moving outside of the park boundaries where we believe they were encountering fishing nets and drowning, and later washing ashore where we would see them,' said Angela Formia of the WCS.

The need for international cooperation The study revealed another critical finding: the tagged turtles spent more than half of their time in the Republic of Congo waters, highlighting the need for international cooperation to protect this species. The Wildlife Conservation Society is now working in conjunction with the national park agencies of both countries to join and expand Mayumba and Conkouati-Douli National Parks, creating what is the first international marine park in the region.

'The proposal to combine and extend the protected areas will be incredibly effective,' said coauthor Brendan Godley, professor at University of Exeter Cornwall and coordinator of the Marine Turtle Research Group. ‘We estimate that 97 per cent of the most critical habitat for this population of olive ridley sea turtles would fall within the expanded park boundaries.'

Coauthor Dan Costa, professor of ecology and evolutionary biology at the University of California, Santa Cruz, said: 'This is a great example of how innovative science on the ecological needs of wide-ranging, long-lived marine species can help justify regional collaborations for effective conservation.'

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