A first multi-sensor gear-based characterisation of the behaviour of target and bycatch species during pelagic longline capture
Abstract
Little is known about the behaviour and stress responses of animals captured by longline gear from hooking until retrieval at the vessel, despite the importance of this process for bycatch mitigation and post-release survival. Most existing studies have relied on physiological sampling at haulback, which provides only a snapshot of stress at retrieval and requires invasive handling. This study used a custom multi-sensor data logger, the SMARTSNAP device, attached directly to the longline to continuously record the behaviour of individuals captured on commercial pelagic longlines in the Gulf of Lion and around Réunion Island between 2022 and 2023. A total of 40 individuals across 15 species, including target tuna species and elasmobranch bycatch, were recorded from hooking until retrieval. Within active capture phases, individual dive sequences were identified and characterised through metrics describing dive duration, depth, descent speed, and directional movement. Atlantic bluefin tuna showed a marked decline in fight intensity over successive dives, whereas blue shark and pelagic stingray displayed more stable patterns. Principal component analysis revealed that individuals which ultimately died following capture were characterised by elevated movement and depth metrics, while surviving individuals showed comparatively lower values. Similar mortality-associated behaviours were observed in other tuna species. These findings support the hypothesis that behavioural dynamics can serve as a proxy of capture-induced exhaustion, demonstrating the potential of gear-based instrumentation to directly assess animal condition during capture. Further work is needed to determine whether these observations can be translated into practical applications for bycatch mitigation, rapid release strategies, and the management of capture-related stress, with potential implications for animal welfare and flesh quality.
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BibTeX
@article{landreau2026first,
title = {{A first multi-sensor gear-based characterisation of the behaviour of target and bycatch species during pelagic longline capture}},
author = {Antoine Landreau and Vincent Kerzérho and Olivier Derridj and Bertrand Wendling and Nolwenn Cosnard and Amaury Boguais and Paul Leloup and Paulo Pimenta and Sylvain Bonhommeau and Jérémie Chanut and Anne-Elise Nieblas and Tristan Rouyer},
journal = {Fisheries Research},
year = {2026},
month = oct,
doi = {10.1016/j.fishres.2026.107892},
url = {https://hal-lirmm.ccsd.cnrs.fr/lirmm-05796832v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - A first multi-sensor gear-based characterisation of the behaviour of target and bycatch species during pelagic longline capture
AU - Antoine Landreau
AU - Vincent Kerzérho
AU - Olivier Derridj
AU - Bertrand Wendling
AU - Nolwenn Cosnard
AU - Amaury Boguais
AU - Paul Leloup
AU - Paulo Pimenta
AU - Sylvain Bonhommeau
AU - Jérémie Chanut
AU - Anne-Elise Nieblas
AU - Tristan Rouyer
PY - 2026
DA - 2026/10/13
JO - Fisheries Research
DO - 10.1016/j.fishres.2026.107892
UR - https://hal-lirmm.ccsd.cnrs.fr/lirmm-05796832v1
AB - Little is known about the behaviour and stress responses of animals captured by longline gear from hooking until retrieval at the vessel, despite the importance of this process for bycatch mitigation and post-release survival. Most existing studies have relied on physiological sampling at haulback, which provides only a snapshot of stress at retrieval and requires invasive handling. This study used a custom multi-sensor data logger, the SMARTSNAP device, attached directly to the longline to continuously record the behaviour of individuals captured on commercial pelagic longlines in the Gulf of Lion and around Réunion Island between 2022 and 2023. A total of 40 individuals across 15 species, including target tuna species and elasmobranch bycatch, were recorded from hooking until retrieval. Within active capture phases, individual dive sequences were identified and characterised through metrics describing dive duration, depth, descent speed, and directional movement. Atlantic bluefin tuna showed a marked decline in fight intensity over successive dives, whereas blue shark and pelagic stingray displayed more stable patterns. Principal component analysis revealed that individuals which ultimately died following capture were characterised by elevated movement and depth metrics, while surviving individuals showed comparatively lower values. Similar mortality-associated behaviours were observed in other tuna species. These findings support the hypothesis that behavioural dynamics can serve as a proxy of capture-induced exhaustion, demonstrating the potential of gear-based instrumentation to directly assess animal condition during capture. Further work is needed to determine whether these observations can be translated into practical applications for bycatch mitigation, rapid release strategies, and the management of capture-related stress, with potential implications for animal welfare and flesh quality.
SN - 0165-7836
SN - 1872-6763
ER -