Characterization Of The Spatial And Temporal Dynamics Of Drifting Fish Aggregating Devices Fads Used By The French Fleet Of Purse Seiners In The Atlantic And Indian Oceans

Characterization of the Spatial and Temporal Dynamics of Drifting Fish Aggregating Devices (FADs) Used by the French Fleet of Purse Seiners in the Atlantic and Indian Oceans

We analyzed the spatio-temporal dynamics of drifting Fish Aggregating Devices (FADs) used by the French purse seine fleet targeting tropical tunas in the Indian and Atlantic Oceans. First, GPS buoys positions used between January 2007 and December 2010 were separated into two categories: at sea positions and on board positions. Five classification methods (velocity filter, k nearest neighbors, Multiple Logistic Regression, Artificial Neural Network and Random Forest) were developed and compared using an already classified subset of buoys positions (2.3%). On the basis of several performance indicators (e.g. accuracy and precision), the Random Forest model was selected as the best classification method and used for predicting the class of the remaining buoys positions. Basin-scale spatial patterns of fishing sets on FADs, as derived from the FAD trajectories, were consistent with logbook data. A strong seasonality in the use of FADs was shown in the Indian Ocean, the highest FAD densities being observed in March in the Mozambique Channel and in August off the Somali coast. By contrast, the French purse seiners operating in the Atlantic Ocean use less FADs and in a rather constant way over the year. Finally, we evaluated of two time-closure areas, the Picolo zone and the IOTC-Somali area and the Chagos Archipelago Marine Protected Area (MPA). Although preliminary, our findings tend to indicate that the closure of that the closure of the IOTC-Somali zone may not represent an efficient protection of the tropical tuna species targeted with FADs.

Canadian Journal of Fisheries and Aquatic Sciences

Assessing the Management of Drifting Fish Aggregating Devices (dFADs) Used to Harvest Tunas in the Atlantic, Pacific, and Indian Ocean