Reliance and usage of anchored Fish Aggregating Devices (aFADs) in the Indonesian tuna fisheries

The development of tuna fisheries in the Indian Ocean is closely linked to the use of Fish Aggregating Devices (FADs). While FADs increase fishing efficiency, their sustainability raises concerns. Information on FAD utilization, particularly in Indonesia, remains limited. This study investigates Indonesia's anchored FADs (aFADs) tuna fisheries through a semi-structured survey of 293 tuna fishers using FADs in eight major Indonesian fishing ports in the Indian Ocean. With the exception of one group of handline vessels that use lights to attract tuna and operate at night, all other groups (purse seiners, troll-line, and handline vessels) utilize aFADs in over 90 % of their tuna-targeted fishing operations. All aFADs were reported to be privately owned, either by vessel captains, vessel owners, fishing associations, or companies, with aFAD sharing primarily occurring within the same aFAD ownership group. On average, vessels or groups of vessels owned between 1 aFAD (hook and line vessels) to 8 aFADs (purse seiners). aFAD arrays reported by respondents showed an average of 4–5 aFADs within 10 nm of the aFADs they utilize. Long aFAD lifetimes (2–4 years on average) indicated the skilled knowledge of fishers in using and maintaining these devices. Interestingly, the number of aFADs visited by fishing vessels was not correlated with the trip duration and remained relatively low (< 16 aFADs visited for all vessels). This suggests that vessels tend to exploit the same aFAD array throughout their trip, even when it lasts several months. Landing data supported these findings and revealed seasonal patterns in aFAD use, including partial shifts in target species for hook and line vessels. The findings of this study are expected to provide quantitative insights and contribute to the sustainable management of tuna FAD fisheries in Indonesia and the Indian Ocean. • Indonesia figures among the largest contributor of the tropical tuna production in the Indian Ocean. • Indonesian tuna fishers; specially purse seine and hook and line heavily rely on the use of anchored fish aggregating devices (aFADs). • aFADs in Indonesia are predominantly privately owned by fishers,vessel owners and company. • aFADs tend to have a longer lifespan compare to dFADs.