Identifying partners at sea from joint movement metrics of pelagic pair trawlers

Type Article
Date 2021-08
Language English
Author(s) Joo RocíoORCID1, 2, 3, Bez NicolasORCID4, Etienne Marie-Pierre5, Marin Pablo6, Goascoz Nicolas7, Roux Jerome1, Mahévas StephanieORCID1
Affiliation(s) 1 : IFREMER, Unité Ecologie et Modèles pour l’Halieutique, Centre Atlantique, Rue de l'Ile d'Yeu, BP 21105, 44311 Nantes Cedex 03, France
2 : Department of Wildlife Ecology and Conservation, Fort Lauderdale Research and Education Center, University of Florida, Fort Lauderdale, FL, USA
3 : Global Fishing Watch, Research and Innovation Team, Washington, DC 20036, USA
4 : MARBEC, Univ Montpellier, IRD, Ifremer, CNRS, Sète, France
5 : Univ Rennes, Agrocampus Ouest, CNRS, IRMAR—UMR 6625, F-35000 Rennes, France
6 : Instituto del Mar del Perú (IMARPE), Chucuito, Callao, Peru
7 : IFREMER, Laboratoire de Technologie et de Biologie Halieutique, Station de Lorient, 8, rue François Toullec, 56100 Lorient, France
Source Ices Journal Of Marine Science (1054-3139) (Oxford University Press (OUP)), 2021-08 , Vol. 78 , N. 5 , P. 1758-1768
DOI 10.1093/icesjms/fsab068
Keyword(s) collective behaviour, dyadic joint movement metrics, fishing tactics, Gaussian mixture model, vessel monitoring system

Here, we present an approach to identify partners at sea based on fishing track analysis, and describe this behaviour in several fleets: pelagic pair trawlers, large and small bottom otter trawlers, mid-water otter trawlers, all in the North-East Atlantic Ocean, anchovy purse-seiners in the South-East Pacific Ocean, and tuna purse-seiners in the western Indian Ocean. This type of behaviour is known to exist within pair trawlers, since these vessels are in pairs at least during their fishing operations. To identify partners at sea, we used a heuristic approach based on joint-movement metrics computed from vessel monitoring system data and Gaussian mixture models. The models were fitted to joint-movement metrics of the pelagic pair trawlers, and subsequently used to identify partners at sea in other fleets. We found partners at sea in all of the fleets except for the tuna purse-seiners. We then analysed the connections between vessels and identified exclusive partners. Exclusiveness was more common in pelagic pair trawlers and small bottom otter trawlers, with 82% and 74% of the vessels involved in partnerships having exclusive partners. This work shows that there are collective tactics at least at a pairwise level in diverse fisheries in the world.

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