International Bottom Trawl Survey (IBTS2021-Q1) - French cruise report.

In 2021, the French NS-IBTS Q1 survey was conducted as part of the International Bottom Trawl Survey program carried out by main countries bordering the North Sea in order to assess abundance and stocks distribution, independently of commercial fisheries data. The first target of the NS-IBTS Q1 survey is to provide a diagnosis on the main commercial fish species by estimating their abundance per age. A standardized protocol is rigorously applied by all participants. The R/V Thalassa sampled the eastern part of the Channel and southern North Sea (until 56° N) from 19th January to 9th February 2021. During daily time, 56 hauls, lasting 30 minutes, have been carried out with a GOV bottom trawl. A total of 82 fish species have been collected, determined and measured, and 2605 otoliths (for age estimation) have been collected for 13 species. This year, whiting (Merlangius merlangus) represented 30% of the total biomass caught followed by herring (Clupea harengus, 26%). During the night, 107 MIK net have been deployed to calculate an index for herring and sprat larvae abundance. Within each station, a CTD sensor was deployed to record environmental parameters (e.g., temperature, salinity and oxygen) all along the water column, from surface to bottom. In order to study the whole marine ecosystem, some additional studies were carried out in the context of the Marine Strategy Framework Strategy and for various research projects.


North sea, GOV, beam trawl, MIK, abundance, stock assessment


55N, 49.3S, 8E, -1W

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Lazard Coline, Verin Yves, Auber Arnaud (2021). International Bottom Trawl Survey (IBTS2021-Q1) - French cruise report. Ref. RBE/HMMN/RH 2021-1. Ifremer.

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