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Leatherback turtles—nearly two meters long and weighing up to 500 kilograms—are built to move. They are the only sea turtle to have tough, ridged, rubbery skin instead of a hard shell, and their streamlined shape and powerful front flippers enable them to swim thousands of kilometers through the open ocean during their migrations.
In their multiyear journeys, leatherback turtles face a variety of lethal threats, from ingesting plastic debris to being caught as by-catch by commercial fishers. Yet the protections leatherback turtles get during various stages of their journeys can vary wildly. According to a new study, leatherback turtles will frequently cross through the waters of as many as 30 different countries, each with its own set of laws and enforcement capabilities.
Leatherback turtles are not the only species to face such shifting protections. In the new paper, Autumn-Lynn Harrison, an ecologist at the Smithsonian Conservation Biology Institute, and her colleagues used tracking data to analyze the movements of 1,648 individual animals from 14 species—from white sharks to sooty shearwaters to leatherbacks. They found that, cumulatively, these animals visit 86 percent of Pacific Ocean countries during their migrations.
The study used data from the Tagging of Pelagic Predators (TOPP) program, which began tracking the movements of predators throughout the Pacific Ocean in 2000. To date, more than 200 scientific studies have been based on this data set.
Bryan Wallace, a marine conservationist at Conservation Science Partners and an expert in global leatherback population dynamics who was not a part of this recent study, lauds the fact that extensive, hard-won data sets like TOPP continue to be put to use to try to answer “tangible questions.” He says Harrison’s study “provides a strong scientific foundation for the more challenging geopolitical and resource management discussions.”
The international travel of leatherbacks and other marine species makes conservation efforts challenging, Harrison says. Coastal nations pass laws to exploit or protect marine life, but these regulations only extend up to 370 kilometers from each country’s shoreline in what is called its exclusive economic zone (EEZ). Outside of EEZs lie the high seas, a global commons that is one of the least protected areas on Earth—and one in which the studied species spend the majority of their time.
Wallace points out that in the high seas, technologies designed to reduce by-catch, such as circle hooks, are not required, though some fleets and boats do use them. In contrast, other areas have stringent regulations—such as near the leatherback turtle nesting beaches in Las Baulas National Marine Park, on the northwest coast of Costa Rica, where fishing of any sort is prohibited.
Harrison presented her research at the recent United Nations meeting in New York, where diplomats were negotiating the world’s first legally binding treaty for the high seas. She says she left the meeting feeling optimistic. “There wasn’t complete consensus on whether there needs to be global oversight, but I did feel a pretty overwhelming sense that, globally, nations know that something needs to change in the high seas.”
Harrison hopes her research will provide critical information for designing international agreements to protect at-risk species as they travel through multiple jurisdictions and across the open ocean.