Spies of the deep: An animal-borne active sonar and bioluminescence tag to characterise mesopelagic prey size and behaviour in distinct oceanographic domains

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Chevallay, Mathilde, Jeanniard Du Dot, Tiphaine, Goulet, Pauline, Fonvieille, Nadège, Craig, Cassandra, Picard, Baptiste, Guinet, Christophe
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Aix Marseille Université, IRD, Université de Toulon, CNRS, Mediterranean Institute of Oceanography (MIO), UM 110, 13288 Marseille cedex 9, France (IRD-MIO), Centre de Recherches sur la Cognition Animale - UMR5169 (CRCA), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2024
• Subjects: Southern elephant seals; Mirounga leonina; Mesopelagic; Myctophids; Biologging; Southern elephant seals Mirounga leonina Mesopelagic Myctophids Biologging; [SDE]Environmental Sciences; Elephant Seals; Southern Elephant Seals
• Online Access: https://hal.science/hal-04361222; https://doi.org/10.1016/j.dsr.2023.104214

International audience Mesopelagic fishes, a central component of marine trophic networks, play a fundamental role in marine ecosystems.However, as they live in highly inaccessible environments, little information is currently available ontheir distribution and abundance. The emergence of biologging technologies has made it possible to use deepdivingpredators as bio-samplers of their environment in under-sampled regions. In this work, we deployed aninnovative miniaturised sonar tag that combines active acoustics with high-resolution GPS, pressure, movementand light sensors on Southern elephant seals, a deep-diving predator feeding on mesopelagic prey. Seals werealso equipped with Conductivity-Temperature-Depth tags. Salinity and temperature depth profiles were used todefine oceanographic domains, allowing us to explore distribution and ecology of mesopelagic prey targeted byseals and the seals’ foraging behaviour. We highlighted strong vertical differences in prey characteristics andbehaviour, with larger, more evasive and less bioluminescent prey in deeper waters. Moreover, prey encounteredin warmer waters were found deeper, were more evasive and displayed a more marked diel vertical migrationbehaviour compared to prey encountered in colder waters, suggesting that prey accessibility and characteristicsdiffer according to oceanographic domains. This study highlights the usefulness of the sonar-bioluminescence tagto infer mesopelagic prey distribution and habitat when deployed on deep-diving predators such as elephantseals.