Swimming behaviour of fish schools in the North Sea during acoustic surveying and pelagic sampling trawling
Working paper
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http://hdl.handle.net/11250/104701Utgivelsesdato
1990Metadata
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This report is not to be cited without prior reference to the authorsSammendrag
Swimming behaviour of schooling herring, mackerel and sprat, when
approached by a survey vessel, was observed by aid of a true motion sonar.
Observations were made both during surveying and during pelagic trawling.
Horizontal swimming speed was clearly length dependent, but there were great variations from one school to another, even if the school members
were of similar size. Generally the schools seemed to be guided by the
approaching vessel, but often the schools avoided the path of the vessel.
An attempt is made to quantify the influence of vessel-avoidance and upper
blind zone distribution on the total abundance estimate. By taking
advantage of the guiding effect, and modifying the gear rigging, the
capture success of the pelagic sampling trawl was clearly increased.