Report of the International Bottom Trawl Survey Working Group (IBTSWG). 27-30 March 2012. Lorient, France

Type Expertise
Date 2012
Language English
Ref. ICES CM 2012/SSGESST:03
Other localization
Author(s) ICES
Contributor(s) Salaun Michele, Verin Yves, Mahe Jean-Claude
Sponsor CIEM / ICES
Abstract The International Bottom Trawl Working Group (IBTSWG) met in Lorient, France, from 27–30 March 2012. There were 21 participants from 12 countries, all of whom are involved in designing and conducting bottom trawl surveys, and one participant representing the ICES Secretariat.
All terms of reference have been met, details are given in relevant sections (see table of contents). Major developments, achievements and recommendations from the 2012 meeting are given below:
Section 3 is dedicated to reviewing the recommendations of the previous year, split into two sections: follow up of recommendations from IBTSWG in 2011; and secondly to answer recommendations for IBTSWG from other EGs.
Individual surveys coordinated by IBTSWG are presented using the standard reporting format that summarizes the surveys design and coverage as well as aggregated results and samples collected for the target species, including summary tables that report samples collected under the DCF (Data Collection Framework). Section 4 and the summary tables provide a centralized and accessible overview of specific survey datasets for those using the data. Also this year IBTS first has provided the first combined index within the Western and southern areas, using Irish groundfish survey and French EVHOE survey data to produce a combined index for cod and haddock on the Celtic Sea area (ICES Division VIIjgh). These indices have been evaluated and accepted by the ICES benchmark process. Maps showing the distribution of the main target species over the entire IBTS coordinated area are presented as combined results for all surveys (see Section 4.4 and Annex 6).
Section 5 deals with the effect of sweep length on net geometry and provides a comparison of net geometry results for GOV gears from different vessels highlighting that differences with the manual expected geometry are produced independently of sweep length. This stresses the recommendation in the manual: ‘gear net geometry, consistent between countries and year’ should be the first aim and the warp/depth ratio should adjusted consequently during the survey’. Results of paired hauls carried out by Marine Scotland Science will be published in the latter half of 2012 and will be made available for discussion to North Sea Survey participants and coordinators before NSIBTS Q1 2013 surveys.
Section 6 about sensitivity of abundance indices looks at two approaches to essentially the same issue – variability of survey indices due to planned or un-planned changes in survey sampling or design. A forced change of vessel for the Swedish survey is used to illustrate the measurable change in sampling unit that can occur with an evolving survey, as well as predict possible scale of impact on the indices going forward. Conversely, a recommendation from WGWIDE to evaluate the potential for an IBTS Horse Mackerel Index for the North Sea is used as an example of taking a historically noisy index and seeing if it can be improved in retrospect using available survey information.
Section 7 deals with quality of the data stored in DATRAS, pointing out some problems detected in relation to DATRAS download products and with the data uploaded in the last year. Problems found resulted in a recommendation to close the download option of some products in DATRAS, and highlights once again the necessity of checking products and algorithms used both when uploading data and when calculating the products. A course of action is proposed to solve these problems.
Section 8 deals with the updates of IBTS manuals (North Sea and Eastern areas) together with the MIK manual, new editions of the current versions will be issued online in the ICES website, with an ISSN assignment and consecutive numbering under this new system. A short summary of the updates to be issued is also presented.
Section 9 addresses the use of IBTS data in the Marine Strategy Framework Directive including again coverage and issues with sampling marine litter within IBTSurveys, an update from WGISUR last meeting and possibilities to build Ecosystem surveys from IBTSurveys.
Finally Section 10 presents the views of the group on the proposal for multi-annual ToRs and the implications of how it can be implemented in the case of the IBTSWG.
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How to cite 

ICES (2012). Report of the International Bottom Trawl Survey Working Group (IBTSWG). 27-30 March 2012. Lorient, France. CIEM / ICES, Ref. ICES CM 2012/SSGESST:03, 329p.