Giant leatherback sea turtles swim from nesting sites in the Solomon Islands and Papua New Guinea all the way across the Pacific Ocean to the coast of California in search of food.These long-distance migrations mean more international cooperation is needed to preserve the critically endangered reptiles, according to a pair of NOAA scientists who used satellites to track the turtles for 10 years.
Conservation efforts at beach nesting sites are only part of the equation, the researcher said, explaining that the turtles have to protected from other threats in foraging areas.
"Tracking the turtles on their extraordinary migrations over the years has allowed us to finally piece together the complex linkages between their breeding areas and feeding areas," said senior author Peter Dutton, with NOAA Fisheries Service. "The leatherbacks have acted as international ambassadors, leading us to join with partners on both sides of the Pacific in a concerted effort to conserve leatherbacks."
"The turtles nesting at Papua Barat (Indonesia), Papua New Guinea, and other islands in our region depend on food resources in waters managed by many other nations for their survival," said Ricardo Tapilatu from the State University of Papua (UNIPA). "It is important to protect leatherbacks in these foraging areas so that our nesting beach conservation efforts can be effective."
Female leatherbacks lay their eggs on tropical nesting beaches before migrating to foraging areas around the world to feed on jellyfish. Leatherbacks are seasonal visitors to the west coast, including the central California coast, traveling across the Pacific and arriving in late summer and fall to forage on large aggregations of brown sea nettles (Chrysaora fuscescens). Click here to visit the NOAA sea turtle photo gallery online.
The study is based on data from 126 leatherbacks tracked by satellite. It was published last week in the journal Ecosphere.
The western Pacific nesters foraged not only in distant temperate ecosystems of the North Pacific, but also in temperate and tropical Large Marine Ecosystems of the southern hemisphere and Indo-Pacific seas.
"We discovered a much greater diversity of foraging behavior than previously thought for Pacific leatherbacks," Benson said. "The foraging areas we identified exhibited a wide range of oceanographic features, including mesoscale eddies, coastal retention areas, current boundaries, or stationary fronts, all of which are known mechanisms for aggregating leatherback prey."
The paper also identifies foraging areas in the East Australia Current Extension and the Tasman Front, drawing attention to the potential threat from the intense fishing by international fleets in these waters.
Leatherbacks (Dermochelys coriacea) are the largest of all marine turtles, weighing up to 2,000 pounds and measuring almost six feet in length. The demise of several leatherback populations around the Pacific has been caused by extensive harvesting of eggs and breeding females on the nesting beaches by indigenous populations, as well as accidental capture in fishing operations. Some of the last remaining Pacific nesting populations are found in the western Pacific in Indonesia, Solomon Islands and Papua New Guinea.
Protecting and rebuilding leatherback sea turtle populations has been a priority for NOAA since 2000, when they were listed under the Endangered Species Act. The NOAA Marine Fisheries Service restricts commercial fishing in large areas north of Hawaii and off the United States west coast because of concern over accidental by-catch of leatherbacks, and has been working to revise which areas are designated as critical habitat for the turtles. They are also listed as critically endangered by the IUCN.
"Our telemetry data will help us develop better analytical models to help fisheries managers predict when and where leatherbacks might be found in areas targeted for fishing," said Tomoharu Eguchi with NOAA Fisheries, a co-author of the paper.