Spotila is the Betz Chair Professor of Environmental Science in the College of Arts and Sciences. He specializes in physiological, biophysical and conservation biology.
Leatherbacks are the widest-ranging marine turtle species and are known to migrate across entire ocean basins. These long-distance migrations are likely to increase the risk that these animals may be caught in fishing gear, undermining conservation efforts to protect turtles on their nesting beaches. Interaction with fisheries is believed to be a major cause of death, which is of particular concern in the eastern Pacific Ocean, where the number of leatherback turtles has dropped by more than 90 percent since 1980.
“Leatherback turtles are long-lived animals that take a long time to reach maturity, so when they are killed in fishing gear it has a huge impact on the population,” said Spotila. “Their numbers are declining so rapidly it is critical that measures are taken quickly to ensure these animals don’t go extinct.”
Spotila and his colleagues used state-of-the art satellite tracking, the largest satellite telemetry data set ever assembled for leatherbacks, to track 135 turtles. The study found that the western Pacific population traveled to many different feeding sites. This wide dispersal allows for a greater likelihood to find food. It also means that the turtles are more vulnerable to being caught unintentionally by fishing gear in coastal and offshore areas.
The eastern Pacific population had a very different migration pattern, traveling from their nesting sites in Mexico and Costa Rica to the southeast Pacific. These turtles tended to feed in offshore upwelling areas where their food, almost exclusively jellyfish, may be concentrated. The more limited feeding areas of the east Pacific turtles makes them more vulnerable to any changes that occur to the distribution or abundance of jellyfish. Deaths caused by human activities, such as being caught in fishing gear, also pose a greater risk of causing this population to go extinct because they have a smaller range than the western leatherbacks.
Said Helen Bailey of the University of Maryland, lead author of the study: “This information … is essential for identifying hot spots and assessing where limiting fishing at particular times of year may be effective for protecting leatherbacks.”