A three level pelagic trawl for near surface sampling of juvenile fish
Working paper
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http://hdl.handle.net/11250/105127Utgivelsesdato
1993Metadata
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This report is not to be cited without prior reference to the authorsSammendrag
In the northeast Atlantic Ocean catch rates of juvenile fish from pelagic trawls are used to
calculate indices of relative abundance which are applied as a first indication of year class
strength. A major constraint for a reliable time series of these indices may arise from a varying vertical fish distribution, particularly near the surface due to sampling gear behaviour.
In this paper a new three level trawl, which samples three separate depths simultaneously, is
described in detail and catches are compared with catches from a standard juvenile survey
trawl. The new trawl was highly more efficient in catching small juveniles in the near surface
layers than the standard trawl. We concluded that changes in densities in this layer could significantly
affect the reliability of the catch data from the standard trawl.