Modeling drifting fish aggregating devices (FADs) trajectories arriving at essential oceanic and coastal habitats for leatherback and hawksbill turtles in the Pacific Ocean
Purse seine fishers using drifting Fish Aggregating Devices (dFADs) to aggregate and catch tropical tuna, deploy an estimated 46,000 to 65,000 dFADs per year in the Pacific Ocean. Major problems associated with this widespread fishing device are i) the potential entanglement of vulnerable marine fauna in dFAD netting and ii) marine pollution, with potential ecological damage via stranding on coral reefs, beaches, and other essential habitats. To explore and quantify the potential connectivity between dFAD deployment areas and important oceanic or coastal critically endangered leatherback (Dermochelys coriacea) and hawskbill (Eretmochelys imbricata) sea turtle habitats in the Pacific Ocean, we conducted passive-drift Lagrangian experiments using simulated dFAD drift profiles. Some connectivity between equatorial areas of dFAD deployments and essential sea turtle habitats was identified, although it was reduced when considering only areas where dFADs are currently deployed. Potential at-risk hotspots of dFAD interaction with sea turtle habitats are i) the migration and leatherback feeding habitats in the tropical southeastern Pacific Ocean; ii) leatherback and hawskbill coastal habitats in the western Pacific (Indonesia, Papua New Guinea, and the Solomon Islands); iii) a large equatorial area south of Hawaiʻi, important for leatherback turtle foraging. Additional research is needed to better understand the entanglements of sea turtles with dFADs at sea and to quantify the likely changes in connectivity and distribution of dFADs under new management measures, such as using alternative dFAD designs that degrade, or changes in deployment strategy.