It's a Mystery Why Hundreds of Sea Turtles Are Dying - or Maybe Not
Dozens of sea turtles, some with signs of concussions, have been washing up on the Pacific coasts of Costa Rica, Nicaragua, EL Salvador and elsewhere in Central America. Researchers in Costa Rica suspect that the culprit is seasonal red tides, which secrete a potent neurotoxin. But conservationists suspect the turtles may have gotten caught in trammels, large commercial fishing nets.
The turtles, some from endangered species and some still alive, are washing up in the hundreds on beaches in Central America. From late September to the middle of October, 114 sea turtles - black turtles (Chelonia agassizii), Olive Ridley turtles (Lepidochelys olivacea) and some that were a cross between the two - have been found on the beaches of El Salvador. 280 have been found so far this year in Costa Rica, 115 in Guatemala and an undisclosed number in Nicaragua. In late 2012, 200 were found dead on Panama's beaches.
Nestor Herrera, the head of wildlife and ecosystems at the Salvadoran environment ministry, thinks that saxitoxin, which is produced by red tide and affects the nervous system, is a likely reason. Saxitoxin, he says, caused the death of about 500 sea turtles in El Salvador in 2006; dogs who ate dead turtles "stopped breathing and died almost instantly."
As Angel Ibarra, coordinator of Ecological Unity of El Salvador, points out, a red tide occurs every year, yet such high number of turtle deaths have not been recorded.
Could Commercial Fishing Be Causing Turtle Deaths?
That's one reason that conservation activists have been increasingly concerned that human activity could be a cause of the turtle deaths. Several dead turtles found near the Murciélago archipelago, in Costa Rica's northwestern province of Guanacaste, were "attached to longline hooks, nylon strings and rope ," Didiher Chacón, the director of the Wider Caribbean Sea Turtle Network (Widecast), tells the Tico Times. As he comments,
"It is not difficult to conclude that they were caught by longline fishing devices. Last week, we had reports of Mahi Mahi in the area, and behind them usually comes the longline fishing fleet."
Hundreds of dead turtles were also found in Gulf Dulce, in the southern Pacific area of Costa Rica, in January of this year. Veterinarians who examined the dead turtles found that they had inflammation and that their respiratory systems were damaged, "leading them to determine the turtles had drowned after being snared in nylon fishing lines, which use several hooks and live bait."
Guatemala's National Council of Protected Areas also says that some turtles are being caught by industrial-size fishing boats. In a practice called trawling, these ships drag huge nets along the bottom of the sea floor that catch anything in their path. Equally hazardous for turtles is drill net fishing, in which long nets are pulled behind ships and near the water's surface.
Widecast and other conservationists say that the frightening number of sea turtle deaths is more than enough reason to push for sustainable fishing practices and to reduce bycatch in commercial fishing. Every year, bycatch fishing procedures end up netting some 30,000 sea turtles including endangered green sea turtles, says Widecast.
If human activity is even contributing to the deaths of sea turtles, it is imperative to minimize this as much as possible. The mortality rate for juvenile sea turtles is already extremely high. As Antonio Benavides, a turtle conservationist in El Salvador, underscores, only one out of the thousands of turtles that hatch from a nest ever returns to the beach it was born at to lay eggs.
On the other side of the world, almost 1,000 turtles were confiscated in a Thai airport last week; a Pakistani man has been arrested. All the turtles found - 470 black pond turtles, 423 radiata turtles and 52 Hamilton turtles - are endangered. Clearly we humans have a huge liking for turtles. Since we do, should we not be making every effort to preserve them and their habitats?