title: Large-Scale Examination of Spatio-Temporal Patterns of Drifting Fish Aggregating Devices (dFADs) from Tropical Tuna Fisheries of the Indian and Atlantic Oceans.
abstract: Since the 1990s, massive use of drifting Fish Aggregating Devices (dFADs) to aggregate tropical tunas has strongly modified global purse-seine fisheries. For the first time, a large data set of GPS positions from buoys deployed by French purse-seiners to monitor dFADs is analysed to provide information on spatio-temporal patterns of dFAD use in the Atlantic and Indian Oceans during 2007-2011. First, we select among four classification methods the model that best separates "at sea" from "on board" buoy positions. A random forest model had the best performance, both in terms of the rate of false "at sea" predictions and the amount of over-segmentation of "at sea" trajectories (i.e., artificial division of trajectories into multiple, shorter pieces due to misclassification). Performance is improved via post-processing removing unrealistically short "at sea" trajectories. Results derived from the selected model enable us to identify the main areas and seasons of dFAD deployment and the spatial extent of their drift. We find that dFADs drift at sea on average for 39.5 days, with time at sea being shorter and distance travelled longer in the Indian than in the Atlantic Ocean. 9.9% of all trajectories end with a beaching event, suggesting that 1,500-2,000 may be lost onshore each year, potentially impacting sensitive habitat areas, such as the coral reefs of the Maldives, the Chagos Archipelago, and the Seychelles.
authors.affiliation: Institut de Recherche pour le Développement, UMR MARBEC (CNRS/IRD/Ifremer/UM2), Avenue Jean Monnet, Sète Cédex France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Maufroy
authors.affiliation: Institut de Recherche pour le Développement, UMR MARBEC (CNRS/IRD/Ifremer/UM2), SFA, Fishing Port, Victoria, Seychelles.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Chassot
authors.affiliation: Institut de Recherche pour le Développement, UMR MARBEC (CNRS/IRD/Ifremer/UM2), Avenue Jean Monnet, Sète Cédex France; IMARPE, Esquina Gamarra y General Valle S/N Chucuito, Callao, Lima, Peru.
authors.forename: Rocío
authors.initials: R
authors.lastname: Joo
authors.affiliation: Institut de Recherche pour le Développement, UMR MARBEC (CNRS/IRD/Ifremer/UM2), Avenue Jean Monnet, Sète Cédex France; Virginia Institute of Marine Science, College William and Mary, Gloucester Point, Virginia, United States.
authors.forename: David Michael
authors.initials: DM
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D005398:Fisheries / Q000295:instrumentation* / Q000379:methods; D019156:Indian Ocean; D008962:Models, Theoretical; D014413:Tuna