Modelling 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) leatherback and hawskbill coastal habitats in the western Pacific (Indonesia, Papua New Guinea, and the Solomon Islands); ii) a large equatorial area south of Hawaiʻi, important for leatherback turtle foraging; and iii) the migration and leatherback feeding habitats in the tropical southeastern Pacific Ocean. 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. We invite WCPFC-SC19 to: ● Note the results on potential connectivity between known areas of dFAD deployment and sea turtle habitats in the central equatorial Pacific, archipelagic areas of the western warm pool, and the southeast Pacific Ocean gyre. Connectivity is large for all equatorial zones though is reduced when dFAD deployment/density hotspots are used to seed virtual dFADs. ● Given the overlap of dFADs with turtles oceanic and coastal habitats, no netting should be used in FAD construction to eliminate potential entanglement. ● Recognize the need for greater knowledge on at-sea interactions between active or abandoned dFADs and at-risk sea turtle populations. ● Support the continued analysis of observed and simulated dFAD trajectories to quantify the likely changes in connectivity and distribution of dFADs within the equatorial fishing grounds and higher latitude sea turtle habitats under proposed fully non-entangling, without netting, and biodegradable dFAD management measures.