"We're seeing a drastic decline," said Chinedu Mogbo, founder of the Greenfingers Wildlife Conservation Initiative, which has rescued and released more than 70 turtles over the last five years after treating them at its turtle sanctuary.

At least five endangered or threatened sea turtle species inhabit Nigeria's waters, but exact numbers are not known and resources for monitoring are inadequate, Mogbo said. His team has rescued Olive Ridley, Hawksbill and Leatherback turtles.

Mostly self-funded, Mogbo's group has been working with local fishermen to save the animals.

"Fishers need income. We offer net repair kits in exchange for rescued turtles or protected nests," he told Reuters at the group's turtle sanctuary in the coastal city of Lagos, Nigeria's commercial capital.

But with no marine protected areas and shrinking nesting grounds, the coastline has become a trap for turtles, Mogbo said, calling for state authorities to do more to protect them.

Nigeria's environmental agency did not respond to requests for comment.

An additional threat to sea turtles comes from brisk demand for their meat, shells and eggs in Nigeria, both for consumption and traditional ritual uses.

"We eat their eggs and sometimes give them to the village elders for voodoo," said Morifat Hassan, who sells fish in the coastal area of Folu on the outskirts of Lagos. Sea turtles fetch up to 90,000 naira ($60) each, Hassan said.

In July, rescuers saved a huge green turtle in the Folu area that was injured after getting tangled in a fishing net. They have named him Moruf.

After negotiating with the fishermen who found Moruf, Mogbo was able to fend off people trying to buy the injured turtle.

"Normally, this turtle would be butchered or sold, but we intervened and will ensure it is returned safely to the sea," Mogbo said as he stood on the shoreline.

($1 = 1,506.2800 naira)