@article{fdi:010049692,
  title = {{W}hen good neighbours become good friends: observing small scale structures in fish aggregations using multibeam sonar},
  author = {{G}erlotto, {F}ran{\c{c}}ois and {J}ones, {E}. and {B}ez, {N}icolas and {R}eid, {D}. {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}onverging results in different scientific fields (behavioural ecology, fisheries biology, acoustic tagging, fisheries acoustics, behavioural modelling) suggest the existence of "micro-groups" inside fish schools. {T}hese would comprise a few (5-10) fish maintaining contact during a period long enough to allow individuals to recognise each other. {I}t is hypothesised that they would prefer to share the space with familiar rather than anonymous conspecifics. {T}o evaluate whether acoustic methods could be used to recognise "micro-structures" inside fish schools and help test the "micro-group" hypothesis we analysed acoustic data from anchovy schools off {P}eru, and gadoids in the {N}orth {S}ea. {D}ata collection used a multibeam sonar ({R}eson {S}ea{B}at 6012). {I}n the {P}eruvian case study, the sonar was mounted set horizontally on a drifting research vessel and the internal structure of the schools of anchovies was analysed, although individual fish could not be discriminated. {I}n the {N}orth {S}ea case study, the sonar was orientated vertically above a demersal trawl to allow observation of individual fish entering the trawl. {G}eostatistical analyses were used to evaluate the existence of small spatial structures in anchovy schools. {I}n these schools, "micro-structures" with a scale as small as 0.5 m were observed acoustically. {F}or the gadoids nearest neighbour distance ({NDD}) measurements were carried out, suggesting that the fish aggregated in small groups (2 to 25 individuals, with an average of 3.7 fish per group) in the trawl catches. {T}he perspectives and limitations of these results are discussed.},
  keywords = {{A}nchovy ; {B}ehaviour ; {G}eostatistics ; {M}ultibeam sonar ; {F}ish school ; {S}patial structure ; {M}icro-group},
  booktitle = {},
  journal = {{A}quatic {L}iving {R}esources},
  volume = {23},
  numero = {2},
  pages = {143--151},
  ISSN = {0990-7440},
  year = {2010},
  DOI = {10.1051/alr/2010017},
  URL = {https://www.documentation.ird.fr/hor/fdi:010049692},
}