No place to hide: accidental captures in longline fishing have been a major factor in driving the leatherback turtle close to extinction. Credit: KENNAN WARD/CORBIS

US marine biologists have drawn a line in the sand. In the face of rapidly dwindling numbers of Pacific leatherback turtles, they have decided that “enough is enough” and are suing the US government for failing to protect the species.

Leatherbacks are endangered throughout the world. But the numbers of the genetically distinct Pacific leatherback turtle are declining precipitously, probably because of their accidental capture by longline fishing. They become entangled in lines or hooks, and some either drown or get picked off by sharks, while many of those released by fisherman later die as a result of their capture.

Although the National Marine Fisheries Service (NMFS), the US government agency responsible for conserving and managing marine resources, recognizes Hawaiian longline fishing as the main threat to the recovery of the leatherbacks under their control, it is now permitting more accidental captures.

Last year, the service authorized an unprecedented take of 244 leatherback turtles, based on a claimed population figure of 85,000 leatherbacks. Critics dispute this population total, as well as the assumption that only a handful of those caught will die. Scientists from the Center for Marine Conservation (CMC) in Washington are now accusing the NMFS of failing to perform its mandatory duties under the US Endangered Species Act.

Pamela Plotkin, a senior conservation scientist at the CMC and the lead scientist in the legal action, says her unit had been in dispute with the NMFS over this issue for several years when it was approached by the Earth Justice Legal Defense Fund, based in Honolulu.

The non-profit law firm works in the area of environmental justice and was looking for plaintiffs to challenge the many unmanaged Hawaiian fisheries. Plotkin agrees that the action is unusual for a group of scientists, but adds: “as you work on different organisms you become passionate and committed and feel it is part of your job to speak out.”

Plotkin has already testified that government figures are incorrect, and several prominent scientists have written to the judge warning him that the number of nesting turtles could be as low as 3,700, and that they are in imminent danger of extinction.

In October last year, the judge ruled that the NMFS had violated the National Environmental Policy Act by allowing a Hawaii-based longline fishery to operate without first completing an environmental impact study. He then closed thousands of square miles of the Pacific Ocean to longline fishing until the study had been completed.

Scientists from Drexel University in Philadelphia and the CMC have now produced a paper (see pages 529–30 ) concluding that the leatherback is on the verge of extinction in the Pacific. Their study population in Costa Rica has fallen from 1,367 nesting females to 117 in ten years. Estimates of annual mortality for this and an important Mexican population are 35 and 20 per cent.

Jim Lecky, the assistant regional administrator for protected resources at the NMFS, says they expect to learn a lot from the lawsuit, but warns: “This is a huge international problem and we could shut down Hawaiian longline fishing tomorrow, and it would not make a dent in this.” Lecky also argues that it would be unfair to put Hawaiian fishermen out of business while other countries would be able to continue fishing. A final decision is due in the next few months.