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|Title: ||When good neighbours become good friends: observing small scale structures in fish aggregations using multibeam sonar|
|Authors: ||Gerlotto, F|
Reid, D G
|Issue Date: ||2010|
|Publisher: ||EDP Sciences|
|Citation: ||Francois Gerlotto, Emma Jones, Nicolas Bez and David G. Reid (2010). When good neighbours become good friends: observing small scale structures in fish aggregations using multibeam sonar. Aquatic Living Resources, 23 , pp 143-151 doi:10.1051/alr/2010017|
|Series/Report no.: ||Aquatic Living Resources;23 (2)|
|Abstract: ||Converging results in different scientific fields (behavioural ecology, fisheries biology, acoustic tagging,
fisheries acoustics, behavioural modelling) suggest the existence of “micro-groups” inside fish schools. These would
comprise a few (5–10) fish maintaining contact during a period long enough to allow individuals to recognise each
other. It is hypothesised that they would prefer to share the space with familiar rather than anonymous conspecifics.
To 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 Peru, and gadoids in the North Sea.
Data collection used a multibeam sonar (Reson SeaBat 6012). In the Peruvian 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. In the North Sea case study, the sonar was orientated vertically above a
demersal trawl to allow observation of individual fish entering the trawl. Geostatistical analyses were used to evaluate
the existence of small spatial structures in anchovy schools. In these schools, “micro-structures” with a scale as small as
0.5 m were observed acoustically. For 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. The perspectives and limitations of these results are discussed.|
|Description: ||© EDP Sciences, IFREMER, IRD 2010.
Available online from http://www.alr-journal.org/
|Appears in Collections:||Peer Reviewed Scientific Papers|
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