@article{fdi:010070286,
  title = {{H}abitat use, vertical and horizontal behaviour of {A}tlantic bluefin tuna ({T}hunnus thynnus) in the {N}orthwestern {M}editerranean {S}ea in relation to oceanographic conditions},
  author = {{B}auer, {R}. {K}. and {F}romentin, {J}. {M}. and {D}emarcq, {H}erv{\'e} and {B}onhommeau, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e investigated the habitat utilization, vertical and horizontal behaviour of {A}tlantic bluefin tuna {T}hunnus thynnus ({ABFT}) in relation to oceanographic conditions in the northwestern {M}editerranean {S}ea, based on 36 pop-up archival tags and different environmental data sets. {T}ags were deployed on early mature {ABFT} (127-255 cm) between {J}uly and {N}ovember in 2007-2014, on the shelf area off {M}arseille, {F}rance. {T}he data obtained from these tags provided 1643 daily summaries of {ABFT} vertical behaviour over 8 years of tag deployment. {B}ased on a hierarchical clustering of this data, we could identify four principle daily vertical behaviour types, representing surface (<= 10 m) and subsurface (10-100 m) orientation, moderate (50-200 m) and deep (>= 200 m) diving behaviour. {T}hese vertical behaviour types showed seasonal variations with partly opposing trends in their frequencies. {A}ccordingly, {ABFT} were more surface orientated during summer, while moderate diving behaviour was more common during winter. {D}epth time series data further revealed inverted day-night patterns for both of these periods. {T}agged {ABFT} frequented the surface waters more regularly during daytime and deeper waters during the night in summer, while the opposite pattern was found in winter. {S}easonal changes in the vertical behaviour of {ABFT} were accompanied by simultaneous changes in environmental conditions ({SST}, chla, thermal stratification). {A}ccordingly, surface orientation and moderate diving behaviour appeared to be triggered by the thermal stratification of the water column, though less pronounced than previously reported for {ABFT} in the {N}orth {A}tlantic, probably indicating adaptive vertical behaviour related to the availability of epipelagic food resources (anchovies and sardines). {D}eep diving behaviour was particularly frequent during months of high biological productivity ({F}ebruary-{M}ay), although one recovered tag showed periodic and unusual long spike dives during summer-autumn, in relation to thermal fronts. {R}egional effects on the vertical behaviour of {ABFT} were identified through {GAM}s, with surface orientation being particularly pronounced in the {G}ulf of {L}ions, highlighting its suitability for an ongoing annual aerial survey program to estimate {ABFT} abundance in this region. {I}n addition, increased levels of mesoscale activity/productivity (e.g. related to oceanic fronts) were detected in an area regularly utilized by {ABFT}, south of the {G}ulf of {L}ions, underlining its attractiveness as foraging ground. {K}ernel densities of geolocation estimates showed a seasonal shift in the horizontal distribution of {ABFT} from this "high-use" area towards the {G}ulf of {L}ions during summer, probably linked to the enhanced availability of epipelagic food resources at this time.},
  keywords = {{T}hunnus thynnus ; {H}abitat use ; {S}pike dives ; {F}ronts ; {T}hermal stratification ; {A}rchival tags ; {MEDITERRANEE}},
  booktitle = {},
  journal = {{D}eep-{S}ea {R}esearch {P}art {II} : {T}opical {S}tudies in {O}ceanography},
  volume = {141},
  numero = {{SI}},
  pages = {248--261},
  ISSN = {0967-0645},
  year = {2017},
  DOI = {10.1016/j.dsr2.2017.04.006},
  URL = {https://www.documentation.ird.fr/hor/fdi:010070286},
}