Preliminary results of an autonomous buoy prototype to count pelagic sharks at FADs

Forget F, Fite C, Yedroudj M, et al (2022) Preliminary results of an autonomous buoy prototype to count pelagic sharks at FADs. In: IOTC - 3rd Ad Hoc Working Group on FADs. IOTC-2022-WGFAD03-11, Online

The fishing grounds of the tropical tuna purse seine fishery are extensive, getting remote information on FADs is crucial to fishers in planning and adapting their fishing strategy. Echo-sounders attached to FADs provide near real-time tuna biomass estimations at FADs and play an important role in the choice of the fishing area and the selection of FADs to visit. Similarly, real time information on the presence of Endangered, Threatened and Protected Species (ETP) species could be helpful to improve fishing selectivity by avoiding certain areas or specific FADs...

An autonomous buoy system prototype (“shark counter”) that has the capacity to detect and enumerate pelagic sharks at FADs automatically using cameras was developed. The automated detection system is based on a deep learning algorithm that was optimised for the shark counter buoy. The general design of the system consists of a floating collar on which the iridium communication system and the solar panels are fixed. The floater is connected to the lower camera platform with carbon fibber poles situated, approximately 1.3 m below the surface, on which 4 IP cameras are fixed (Figure 1). A waterproof housing containing the battery and the microcomputer is fixed onto the carbon poles. Once activated, the buoy will film 10 mins every hour. The shark detection algorithm processes the videos and outputs the number of detected sharks per frame (Figure 2). A CSV file containing the buoy position, the time stamp of the counts, number of sharks per frame and the Nmax (maximum number of sharks per time step) are sent by Iridium and are accessible remotely.