Center for Marine Biodiversity and Conservation

The Pacific Ocean is a highly variable environment, and changes in oceanographic conditions impact the distributions of many organisms. Inter-annual climate variability, especially the El Niño/Southern Oscillation, is known to have wide-ranging impacts on organisms in the California Current. Understanding the factors that drive changes in the spatial ecology of organisms, such as inter-annual climate variability, is essential in many cases for effective conservation. Leatherback marine turtles are endangered, and many populations, especially in the Pacific, are declining due to anthropogenic impacts. This study demonstrates that during positive phases of the El Niño/Southern Oscillation, there is a southward bias to Western Pacific leatherback tracks as they depart the California Current. During autumn when leatherbacks frequent the California Current, the US National Marine Fisheries Service institutes a large time-area closure for the drift gillnet fishery to minimize leatherback bycatch. During positive phase autumn months, this study reveals that much of the leatherback activity occurs south of the time-area closure’s southern boundary where drift gillnet fishing is still permitted. With the southward movements of leatherbacks during positive phase autumn months, this study suggests seasonal dynamic adaptive management measures may be warranted.