The challenge of assessing the effects of drifting fish aggregating devices on the behaviour and biology of tropical tuna

Amaël Dupaix (1) , Frédéric Ménard (2) , John D Filmalter (3) , Yannick Baidai (4) , Nathalie Bodin (5, 6) , Manuela Capello (1) , Emmanuel Chassot (7) , Hervé Demarcq (1) , Jean-Louis Deneubourg (8) , Alain Fonteneau (9) , Francesca Forrestal (10) , Daniel Gaertner (1) , Martin Hall (11) , Kim N Holland (12) , David Itano (13) , David Michael Kaplan (1) , Fabien Forget (1) , Jon Lopez (11) , Francis Marsac (1) , Alexandra Maufroy (14) , Gala Moreno (15) , Jeff A Muir (12) , Hilario Murua (15) , Liliana Roa-Pascuali (16) , Géraldine Pérez (17) , Victor Restrepo (15) , Marianne Robert (18) , Kurt M Schaefer (11) , Grégory Sempo , Marc Soria (1) , Laurent Dagorn (1)

1 UMR MARBEC - MARine Biodiversity Exploitation and Conservation - MARBEC
2 MIO - Institut méditerranéen d'océanologie
3 SAIAB - South African Institute for Aquatic Biodiversity
4 African Marine Expertise
5 SFA - Seychelles Fishing Authority (SFA)
6 SOS - Sustainable Ocean Seychelles
7 IOTC - Indian Ocean Tuna Commission
8 ULB - Université libre de Bruxelles
9 Consulant, Saint-Malo
10 SEFC - Southeast Fisheries Science Center
11 IATTC - Inter-American Tropical Tuna Commission
12 HIMB - Hawai'i Institute of Marine Biology
13 Opah Consulting
14 ORTHONGEL
15 ISSF - International Seafood Sustainability Foundation
16 CLS - Collecte Localisation Satellites
17 Institut Océanographique Paul Ricard, Six-Fours-les-Plages, France
18 DECOD - Dynamique et durabilité des écosystèmes : de la source à l’océan

Fishers have intensively used drifting fish aggregating devices (DFADs) over the last three decades to facilitate their catch of tropical tunas. DFADs increase purse-seine efficiency, potentially increasing tuna fishing mortality. They could also have indirect impacts (unrelated with fishing mortality) and assessing the consequences of their presence at sea on tuna populations is a challenge. The use of DFADs results in a major increase in the number of floating objects, which are spatially heterogeneous at sea. To date, no converging scientific results exist regarding the indirect effects of DFADs on the large-scale movements and behaviour of tuna, mainly due to the difficulty of disentangling the respective roles of DFADs and environmental factors. Some biological indices show that tuna condition is lower when associated to a floating object than in a free-swimming school. However, it is not clear whether this is the cause or the consequence of the association, nor if it has long-term effects on individuals’ fitness. Further scientific progress require (i) the collection of time series of indicators to monitor habitat change, individual behaviour, individual fitness and population dynamics, and (ii) experimental studies to identify the underlying behavioural and biological processes involved in associative behaviour. The extent of the modification of the surface habitat by the massive deployment of DFADs and the current uncertainty of the possible long-term consequences on the individual fitness and dynamics of tuna populations argue for the need for increased awareness of this issue by Regional Fisheries Management Organisations regulating tuna fishing.

Keywords: DFAD; ecological effects; ecological trap; fish behaviour; fisheries management; tuna

Domains: Biodiversity and Ecology; Sciences and technics of fishery

Amaël Dupaix, Frédéric Ménard, John D Filmalter, Yannick Baidai, Nathalie Bodin, et al.. The challenge of assessing the effects of drifting fish aggregating devices on the behaviour and biology of tropical tuna. 2023. ⟨hal-04047298v3⟩