International Bottom Trawl Survey Working Group



IBTSWGIBTSWGTrueKai Ulrich Wieland, Corina ChavesEOSGkw@aqua.dtu.dk, corina@ipma.pt74International Bottom Trawl Survey Working Group

The International Bottom Trawl Survey Working Group (IBTSWG) coordinates fishery-independent multispecies bottom-trawl surveys within the ICES area.

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The main objective of the surveys is the long-term monitoring of demersal fish to provide ICES assessment and science groups with consistent and standardized data:

  1. For examining spatial and temporal changes in the distribution and relative abundance of fish and fish assemblages;

  2. Of commercial fish species for stock assessment purposes.

An expert group coordinating the surveys has been in existence for several decades, but has over time evolved considerably, together with the objectives of the survey itself. While the international programme was originally designed as a young herring survey, the focus has since then widened to cover the demersal stocks in addition to the abundance indices of herring which still complement the indices recorded with acoustical methods in separate surveys. Hence, IBTS data feed into the assessment of both demersal and pelagic stocks. Moreover, the general survey aims have broadened, and the IBTS is now a fundamental source of long-term data on the status of the fish communities in relation to their environment in the ICES area.

The IBTSWG designates survey coordinators for the Q1 and Q3 programmes in the North Sea and Q4 in the northeastern Atlantic area. Coordinators support the annual survey operations and collate the survey data for the relevant assessments. The IBTSWG reports on the annual data obtained and promotes the standardization of gears and methods used. New challenges exist with the evaluation of options survey design adaptation and sampling strategies to simultaneously address upcoming needs for the monitoring of ecosystem components or functions, e.g. in connection to the EU Marine Strategy Framework Directive (MSFD).

By the nature of the broadened tasks, the group strongly depends on participation and invites experts from different disciplines: Survey specialists, assessment experts (who can provide a link to relevant assessment groups), gear technologists, ecosystem modellers, and statisticians.


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