Integrating scientific and French tropical tuna purse seine skippers knowledge for a better management of dFAD fisheries in the Indian Ocean

Since the mid 1990s, the use of drifting Fish Aggregating Devices (dFADs) by purse seiners, artificial objects specifically designed to aggregate fish, has become an important mean of catching tropical tunas. In recent years, the massive deployments of dFADs, as well as the massive use of tracking devices on dFADs and natural floating objects, such as GPS buoys, have raised serious concerns for tropical tuna stocks, bycatch species and pelagic ecosystem functioning. Despite these concerns, relatively little is known about the modalities of dFAD use, making it difficult to assess and manage the impacts of this fishing practice. The present paper provides an overview of a 4-year research on the use of dFADs by tropical tuna purse seiners in the Western Indian Ocean. Though our primary objective was to derive information on dFAD fisheries from a large variety of quantitative sources of information (GPS buoy positions, onboard observers, logbooks and VMS), a multi-disciplinary approach was adopted throughout our research. Quantitative results (estimates of dFAD use, fishing efficiency and impacts of dFAD use) were discussed with French purse seine skippers during semi-structured interviews to understand their perception of the impacts of dFAD use and to propose adapted management options for tropical tuna purse seine dFAD fisheries. Interviews with French purse seine skippers revealed the existence of a competition between EU purse seine fleets, encouraging the recent increase in the use of dFADs. They underlined the need for a more efficient management of the fishery, including the implementation of catch quotas, a limitation of the capacity of purse seine fleets and a regulation of the use of support vessels.