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. Last Updated: 07/27/2016

Fishing Said To Threaten Turtles With Extinction




NEW YORK -- Leatherback turtles, whose numbers in the Pacific have plunged in recent years, will all but disappear within a decade unless commercial fishing practices are changed, according to a new analysis of the giant animals' nesting activity.


The turtles, which nest on beaches and then spend almost all of their lives in the open sea, have been dying in large numbers f at least 1,500 females every year by some estimates f caught in the long lines and nets used by commercial fishers.


This level of mortality, combined with the natural high mortality of turtle hatchlings, means that the population is unsustainable, according to the analysis made on a computer devised by scientists at Drexel University in Philadelphia, who have studied the turtles' nesting activity at a major site in Costa Rica since 1988.


"The rate of adult mortality is too high," said Richard Reina, a marine biologist at Drexel and one of the authors of the study, which was reported in June in the journal Nature. "They just can't recover."


From a high of 1,367 females that nested at Playa Grande, Costa Rica, in 1988, the model forecasts that fewer than 50 will nest by the year 2004, a number that means the turtles will be effectively wiped out in the Pacific Ocean.


Efforts to protect the turtles where they nest will only delay reaching that number by about five years, Reina noted. "Our model always predicted extinction," he said.


Cynthia Lagueux, a zoologist with the Wildlife Conservation Society who is working on a turtle project in Nicaragua, said there was general agreement among scientists that turtle populations were declining, particularly in the Pacific.


Leatherbacks, which can weigh 800 pounds or more and are listed as endangered by the World Conservation Union, return to the same beaches to lay their eggs on average every three years. At Playa Grande, the scientists tagged females to determine whether and with what frequency they returned.


The scientists found that not only were the overall number of nesting turtles declining sharply, but also that the number of returning females fell far below what was expected. The researchers ruled out an increase in the time between nesting as a cause, and conducted aerial surveys of the entire western coastline of Central America to determine that the turtles were not nesting elsewhere.


The only explanation, the researchers said, is that the turtles are dying during the years they migrate throughout the ocean. And although the fishing industry's reports on what is known as the bycatch f unintended victims hauled in along with the fish being sought f tend to be poor, particularly in Asia, the few reports available indicated that leatherbacks were being killed in substantial numbers.


"It really comes down to time and effort," Reina said. "For a commercial fishing boat, time is money. Hooks are money. Nets are money. Turtles are not money."