%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Bauer, R. K.
%A Forget, Fabien
%A Fromentin, J. M.
%A Capello, Manuela
%T Surfacing and vertical behaviour of Atlantic bluefin tuna (Thunnus thynnus) in the Mediterranean Sea : implications for aerial surveys
%D 2020
%L fdi:010079897
%G ENG
%J Ices Journal of Marine Science
%@ 1054-3139
%K abundance index ; archival tags ; surface availability ; thermal stratification ; vertical behaviour
%K MEDITERRANEE
%M ISI:000582719500034
%N 5
%P 1979-1991
%R 10.1093/icesjms/fsaa083
%U https://www.documentation.ird.fr/hor/fdi:010079897
%> https://www.documentation.ird.fr/intranet/publi/2020/11/010079897.pdf
%V 77
%W Horizon (IRD)
%X Atlantic bluefin tuna (Thunnus thynnus) (ABFT) frequently engage in surface basking and foraging behaviour that makes them detectable from afar. This behaviour is utilized for the development of fisheries-independent abundance indices based on aerial surveys, although changes in the surface-feeding dynamics of ABFT are not yet accounted for. We investigated the daytime surfacing behaviour of ABFT at different temporal and vertical resolutions based on 24 individuals (117-158 cm fork length), tagged with pop-up archival tags in the Gulf of Lion, NW-Mediterranean Sea between 2015 and 2016. The results suggest that ABFT remain usually <2 min continuously within the visible surface (0-1 m) during daytime. ABFT presence in the 0-1 and 0-20 m layers varied over time and between individuals but showed a seasonal decline towards autumn with the breakdown of thermal stratification. Furthermore, the rate of surfacing events was highly correlated with the time spent in the 0-20 m layer. Geolocation estimates confirm a strong site fidelity of ABFT during the aerial survey period (August-October) in the Gulf of Lion. Our results support the choice of the survey region and period, but related indices should account for the seasonality of ABFT surface behaviour [i.e. the time spent in the 0-20 m layer.
%$ 040 ; 034