Towards non-entangling and biodegradable drifting fish aggregating devices – Baselines and transition in the world’s largest tuna purse seine fishery

Drifting Fish Aggregating Devices (dFAD) are widely used in purse seine tuna fisheries globally. DFADs are often lost or abandoned by the fishing industry which can lead to marine pollution, entanglement of sensitive species and habitat damage. They are considered as a high-risk lost or abandoned fishing gear due to their common construction with long-lasting synthetic materials, including netting. This study used data collected by fishery observers to investigate materials and designs used in dFAD construction over the last 10 years in the Western and Central Pacific Ocean (WCPO). Results indicated that apart from bamboo, which is commonly used in dFAD rafts with other synthetic materials for buoyancy, very few natural materials are used. The depth of dFAD appendages varied, with a median of 50 m. Most dFADs used netting of various mesh sizes in some aspect of their construction. There is limited information to assess the uptake of lower entanglement risk dFAD designs. Transition towards more environmentally friendly dFAD designs is being promoted by management measures imposed by the Western and Central Pacific Fisheries Commission that include banning of netting by 2024 and encouraging the use of natural materials. Scientific trials are underway to support industry adoption of biodegradable dFAD materials. This paper provides important baseline data to detect and monitor future changes in dFAD construction and materials in response to management measures, and also highlights limitations to data collected by observers that will need to be improved to better monitor these changes.