Understanding Spatial Behaviour of Commercial Fishing Boats Foraging Around Fishing Aggregating Devices in The Southern Philippines

Andre Chagas da Costa Neves

The widespread use of fishing aggregating devices in the Philippines urges regulation due to its elevated bycatch rates of juvenile tuna, and the vertiginous decline in catches of tuna species reported in the Philippine coastal waters during the last decades. In this study, using satellite data, information about the spatial distribution of purse seine fishing is provided in two sites in the southern Philippines. Using geographic information system, some variables were created and evaluated which have more potential to predict when the boats are close to FADs. Moreover, the
searching strategy of the boats was analyzed to assess if they perform movement patterns that maximize efficiency. The results indicated that these boats fish far from the ports, stay long periods in the fishing grounds and the fishing effort is distributed in patches. Movements resembling Lévy
Flights were observed in all boats and areas, close to the theoretical optimum. The best variables to predict the distance to a FAD were the step length and the bounding box. These findings are in agreement with what has been reported in previous interviews, emphasizing the efficiency
achieved by using FADs and providing recommendations to estimate fishing effort using satellite data.