Every summer, Wageningen Marine Research carries out a Beam Trawl Survey in the North Sea on the Tridens research vessel. The primary aim of the Beam Trawl Survey (BTS) is to supply fisheries with independent stock indices and estimates of the age-structure of North Sea plaice (Pleuronectes platessa) and sole (Solea solea, Solea vulgaris).
Researcher Ingeborg de Boois reports in a ship's log from the Tridens:
North Sea plaice and sole
The BTS indices are used by the ICES Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) for stock assessments and recruitment estimation. Both are important data sources for the catch predictions and hence for management advice.
In addition to flatfish, the applied beam trawl also catches benthic ( = bottom dwelling) organisms (e.g. echinoderms, squid, crabs), which are counted. The BTS thus also contributes valuable information concerning the state of the North Sea ecosystem.
The collated biological data comprise the following information:
- length frequency distributions for all fish species
- information on age structure of several flatfish species and cod
The BTS is coordinated by the ICES Working Group on Beam Trawl Surveys (WGBEAM). It is carried out in July-September with an 8 meter beam trawl. In each ICES rectangle 1-4 hauls are carried out.
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