Studying the influence of culture, weather, and policy on night fishing in Southeast Asia using satellite data

Abstract

Southeast Asia’s (SEA’s) data-scarce marine fisheries remain inadequately protected. Since light-assisted fishing gear is widely used in SEA, Visible Infrared Imaging Radiometer Suite (VIIRS) Boat Detections (VBDs) can help plug the data gap by providing a more comprehensive observation of lit offshore boats via remote sensing, thus offering insight into night fishing patterns. To contribute information that can help improve fisheries management, this project used 2012-2021 VBDs of four SEA countries to investigate the influence of public holidays (PHs), tropical cyclones (TCs), and fishery closures (FCs) on night-time fishing activity. Change in fishing activity during an event was quantified by computing the percentage difference in VBDs for PHs and TCs, and the VIIRS Closure Index (VCI) for FCs. Generally, fishing activity was reduced by PHs, TCs, and FCs, albeit to different extents. First, VBDs decreased moderately during traditional new year holidays as fishers would prioritise celebrating these important occasions. Exceptions occurred during seasonal poverty and COVID-19 because fishers could not afford to spend money on festivities. Second, VBDs decreased by various magnitudes during most TCs, corroborating the theory that inclement weather dampens fishing. Outliers indicate fishers staying at sea, possibly due to poor communication and an existing shift in strategy towards longer fishing trips. Third, VBDs decreased minimally during FCs. Mean VCIs ranged from 11% to 46%. Low compliance highlights the persisting issue of illegal fishing, often a consequence of inadequate monitoring, control, and surveillance efforts. This is exacerbated by COVID-19 as travel restrictions have hindered patrol operations.