FN Archimer Export Format PT J TI Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries BT AF Wain, Gwenaëlle Guéry, Lorelei Kaplan, David Gaertner, Daniel AS 1:1,2;2:1,2;3:1,2;4:1,2; FF 1:;2:;3:;4:; C1 MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France Institut de Recherche pour le Développement (IRD), UMR MARBEC, Av. Jean Monnet, CS 30171, Sète Cedex 34203, France C2 IRD, FRANCE IRD, FRANCE UM MARBEC IN WOS Cotutelle UMR IF 3.906 TC 17 UR https://archimer.ifremer.fr/doc/00665/77746/79989.pdf LA English DT Article DE ;catch per unit effort;hyperstability;Indian Ocean;standardization AB Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (⁠≈10%⁠) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase. PY 2021 PD JAN SO Ices Journal Of Marine Science SN 1054-3139 PU Oxford University Press (OUP) VL 78 IS 1 UT 000648942600020 BP 235 EP 245 DI 10.1093/icesjms/fsaa216 ID 77746 ER EF