Drifting Fish Aggregating Devices entering French Polynesia EEZ a modelling approach

The drifting Fish Aggregating Devices (dFADs) are fishing gears that are not used by fishermen in French Polynesia which Exclusie Econimic Zone (EEZ) occupies an area of about 5 million square kilometer. More and more dFADs from foreign purse seiner vessels are found in French Polynesia EEZ as reported by fishermen. Some of them drift through the area and leave the EEZ but some of them strand on islands before damaging the coral reef and may be introducing new species collected during their journey. After an attempt to count the stranded dFADs on some islands, we realize that it is too costly and time consuming, if we have to do the counting on the 118 islands. We proposed here to apply a lagrangian model to follow the drifts of artificial dFADS in order to estimate the number of dFADs that would reach the islands. Because the appendages of the dFADs have various length, three simulations were performed with three velocity fields. Statistics regarding the number of dFADs entering French Polynesia EEZ as well as the number of dFADs stranded on islands are estimated. Most of the stranded dFADs are found in the Tuamotu archipelago for all simulations but with varying numbers. The number of stranded dFADs in the Marquesas archipelago varies considerably between the three simulations while very few changes are observed for the Society and Austral archipelagoes. The impacts of dFADS on the local fishery and on the island environment will be discussed.