@article{fdi:010079388,
  title = {{S}easonal and spatial variability in the vertical distribution of pelagic forage fauna in the {S}outhwest {P}acific},
  author = {{R}eceveur, {A}. and {M}enk{\`e}s, {C}hristophe and {A}llain, {V}. and {L}ebourges {D}haussy, {A}nne and {N}erini, {D}. and {M}angeas, {M}organ and {M}{\'e}nard, {F}r{\'e}d{\'e}ric},
  editor = {},
  language = {{ENG}},
  abstract = {{A}coustic data are an invaluable source of information for characterizing the distribution and abundance of mid-trophic level organisms ({MTLO}s) in the ocean. {T}hese organisms play a key role in the ecosystem as prey of top predators and as predators of lower trophic level organisms, as well as in carbon export from the surface into deeper waters. {T}his study used 38 k{H}z-{EK}60 acoustic echosounder data from six cruises spanning 2011-2017 to explore the seasonal and spatial variability in the vertical distribution of {MTLO}s' from 10 to 600 m in the {N}ew {C}aledonian ({S}outh {P}acific) {E}xclusive {E}conomic {Z}one. {A} total of 16715 acoustic vertical profiles of acoustic backscattering strength were clustered into homogeneous groups. {T}wo small shallow scattering layers ({SSL}s) between 0 and 100 m, and one large deep scattering layer ({DSL}) at around 550 m depth, characterized the mean vertical distribution of {MTLO}s. {A} machine-learning model (e{X}treme {G}radient tree {B}oosting algorithm, {XGB}oost) was fitted to explain the acoustic profile clusters with environmental variables as predictors. {S}un inclination was the most important factor in structuring the vertical profile shapes due to the diel vertical migration signal, followed by the mean oxygen value of the top 600 m. {B}athymetry, euphotic depth, 0-600 m mean temperature and {SST} were the next most significant variables. {I}sotherm depth, surface chlorophyl{D}a, wind, and mean salinity had a lower influence on the shape of the vertical profiles. {T}he model was then used to construct vertical echograms at the scale of the {N}ew {C}aledonian {EEZ}, showing an accuracy up to 87% in cross validation. {A}cross the {EEZ}, the shape of vertical acoustic profiles were comparable, though layer echo intensities varied spatially with a marked north-south gradient that remained relatively constant seasonally. {T}he vertically-averaged acoustic values were characterized by a maximum to the south of the {EEZ} in summer, mainly driven by high oxygen values as well as shallow euphotic depth. {W}e also estimated a migrant proportion between day {DSL} and night {SSL} of about 78%. {O}ur methodology offers a promising approach for analyzing the control of the environment on the vertical distribution of {MTLO}s for other oceanic provinces, while also providing a framework to investigate the corresponding trophic interactions between {MTLO}s and their predators feeding at different depths and times. {M}oreover, our findings stress the need to consolidate knowledge on species composition to optimize acoustic data interpretation.},
  keywords = {{M}icronekton ; {E}chosounder ; {P}acific ocean ; {M}esopelagic zone ; {S}ound scattering layer ; {E}nvironment ; {NOUVELLE} {CALEDONIE} ; {PACIFIQUE}},
  booktitle = {},
  journal = {{D}eep-{S}ea {R}esearch {P}art {II} : {T}opical {S}tudies in {O}ceanography},
  volume = {175},
  numero = {},
  pages = {104655 [16 ]},
  ISSN = {0967-0645},
  year = {2020},
  DOI = {10.1016/j.dsr2.2019.104655},
  URL = {https://www.documentation.ird.fr/hor/fdi:010079388},
}