@inproceedings{fdi:010078282,
  title = {{M}icronektonic acoustic density variations along {B}enguela {C}urrent {L}arge {M}arine {E}cosystem continental shelf from 1994 to 2001 [r{\'e}sum{\'e} de poster]},
  author = {{U}anivi, {U}. and {M}ouget, {A}nne and {P}errot, {Y}annick and {M}igayrou, {C}. and {S}arr{\'e}, {A}. and {K}rakstad, {J}.{O}. and {D}iogoul, {N}. and {D}emarcq, {H}erv{\'e} and {B}rehmer, {P}atrice},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {B}enguela {C}urrent {L}arge {M}arine {E}cosystem ({BCLME}) is situated along the coast of south-western {A}frica, stretching from {T}ombua ({A}ngola) in the north (16°{N}, 11°{W}) southwards to the east of the {C}ape of {G}ood {H}ope ({S}outh {A}frica) (29°{S}, 17°{E}) and includes the study zone, from 17°{S}, 9°{E} to 31°{S}, 17°{E}. {I}n this work, we focused on the {N}amibian continental shelf where fishing activities are mostly due to industrial fishing. {A}coustic data were recorded with a 38 k{H}z echosounder, from 10 to 500 m depth over 8 surveys totalling 46 302 nmi from 1994 to 2001. {T}o get homogenous data (i) only off-upwelling season surveys ({O}ctober to {J}une) were studied and (ii) only continental shelf data were considered (10-150 m). {T}he mean volume backscattering strength ({S}v in d{B}) was used as a micronektonic biomass proxy to assess its spatial inter-annual variability. {D}iel transition periods were removed from analyses to avoid micronektonic density changes bias due to diel vertical migrations. {D}ata were echointegrated at a spatial resolution of 0,1 nmi*1 m depth using the {M}atecho tool. (i) {O}n horizontal dimension, the variability in annual micronektonic densities was assessed using the mean {S}v value for each 0,1 nmi {E}lementary {S}ample {U}nit ({ESU}). {T}hen, hot and cold spots were computed from the combined analysis of the spatial correlation and the {M}oran's {I} index of these values. (ii) {O}n vertical dimension, the change of micronektonic spatial structure between day and night was assessed using the mean {S}v value for each 1 m depth step. {T}he inter-annual variability inside the eastern boundary upwelling ecosystem of the {BCLME} was analysed. (i) {N}o significant change in micronektonic density was observed over the study period. {M}ean micronektonic acoustic density values observed were lower than in other {A}frican {A}tlantic large marine ecosystems. (ii) {H}ot and cold spots were spatially stable over time. {F}urther analysis of physico-chemical parameters should improve the understanding of this pattern. (iii) {A} different vertical structure was reported between day and night, suggesting a migration from bottom to surface at dusk, as in the well-known diel vertical migrations. {I}n perspective, physical processes occurring in the water column from turbulence to mesoscale activities should be considered in future studies.},
  keywords = {{AFRIQUE} {SUBSAHARIENNE} ; {ANGOLA} ; {NAMIBIE} ; {AFRIQUE} {DU} {SUD} ; {ATLANTIQUE}},
  numero = {},
  pages = {154},
  booktitle = {{I}nternational conference {ICAWA} 2017 and 2018 : extended book of abstract : the {AWA} project : ecosystem approach to the management of fisheries and the marine environment in {W}est {A}frican waters},
  year = {2019},
  ISBN = {978-9553602-0-06},
  URL = {https://www.documentation.ird.fr/hor/fdi:010078282},
}