Key Factors Influencing Tuna Association Behavior During Prolonged Drift Periods of Fish Aggregating Devices

ABSTRACT

Drifting fish aggregating devices (DFADs) are widely used in tuna purse seine fisheries, yet the mechanisms underlying tuna association behavior remain insufficiently understood. Based on DFADs trajectory and echosounder buoy data collected in the Western and Central Pacific Ocean from November 2020 to June 2021, this study reconstructed DFADs drift trajectories using an integrated Lagrangian simulation and machine learning framework, and further analyzed the temporal dynamics and key drivers of tuna association behavior based on acoustic observations concentrated around sunrise. The results showed that tuna association intensity gradually increased after DFADs deployment, remained relatively high between Days 15 and 30, and peaked around the 30th drifting day. In addition, tuna association behavior exhibited a potential lunar periodicity, with higher colonization probability occurring after the full moon. Generalized additive models identified sea water salinity, dissolved oxygen, upper‐ocean thermal conditions, and DFADs drift persistence as the dominant factors influencing tuna association behavior. Overall, stable and suitable environmental conditions and directionally persistent drift trajectories were associated with more stable tuna aggregations. These findings provide useful references for optimizing DFADs deployment and supporting sustainable tuna fishery management.