Interim Report of the International Bottom Trawl Survey Working Group. 27-31 March 2017

Type Scientific report
Date 2017
Language English
Ref. ICES CM 2017/SSGIEOM:01
Other localization
Author(s) ICES
Contributor(s) Auber ArnaudORCID, Travers-Trolet MorganeORCID, Laffargue PascalORCID, Verin Yves

The report presents summaries of the national contributions in 2016–2017 and planning for 2017–2018 for the surveys coordinated by the International Bottom Trawl Survey Working Group (IBTSWG). In the North Sea, the surveys are performed in quarters 1 and 3; in the Northeast Atlantic the surveys are conducted in quarters 1, 3, and 4 with a suite of 14 national surveys covering shelf areas from north off Scotland to the Gulf of Cádiz. North Sea Q1, 2017: Seven countries using six different vessels participated and performed 377 valid GOV hauls and 655 valid MIK hauls in the period between 18 January and 24 February. All rectangles were covered by at least 1 GOV haul and only one rectangle was not covered by any MIK haul. Denmark and Sweden both used “DANA” and Norway used “Cefas Endeavour” because “GO SARS” was not available during the time of the survey. All countries used their own survey gear. The almost complete coverage of the area including three additional rectangles (52E9, 52F0, 52F1) in the north was mainly because of the very good weather conditions but also due to the change in the allocation of rectangles to the different countries which reduced steaming time. The Netherlands were not able to execute MIK hauls during a significant part of its survey but most of these stations were covered by other countries. Despite some minor adaptions, no further changes of the survey are planned for 2018. [The allocation of the area had significantly changed for the 2017 Q1. The allocation combined with very favourable weather conditions resulted in almost complete coverage, which was actually the first time in a couple of years despite the reduction in effort. However, as this was largely due to the very good weather conditions it was impossible to evaluate the allocation and to discuss whether further changes are required] North Sea Q3, 2016: Six countries using five different vessels participated and performed 382 valid GOV hauls in period from 15 July to 7 September. Denmark and Sweden used both “DANA” but with their own survey gear. The total number of hauls was the highest ever in the time-series. This was partly because of good weather conditions but also because, as in 2015, a mixture of 15 and 30 min tows was used. Denmark, Germany, Norway, and Scotland participated in this exercise performing between 17% and 43% more hauls than mandatory. No major change in the rectangle allocation scheme between countries is planned but is yet not finally decided whether the use of 15 min tows continues in 2017 survey. [All participants are encouraged to record time to settle and time to haul, in addition to the normal parameters. If time permits, catch information for 0-minute tows (i.e. tows that are hauled as soon as the net settles on the bottom) are desired. Details for recording the additional haul information can be found in section 11.1.6.

Northeast Atlantic 2016: Seven vessels from five countries performed 13 surveys along the Northeastern Atlantic IBTS area. A total of 1066, out of the 1057 hauls planned, were accomplished within 297 days at sea distributed between the first, third and fourth quarters. Tow duration was reduced for UK-NIGFS and Porcupine survey, as proposed in IBTS2016. In both cases catches were reduced and work on board was easier to accomplish while no immediate effect on representability of the samples, while possible effects on length distributions and or taxonomical diversity will be explored. The Irish Anglerfish and Megrim Survey (IE-IAMS) has been included in this report as agreed in last year’s meeting.

The IBTSWG has produced three manuals, the manual for the North Sea IBTS and the Northeast Atlantic IBTS as well as the manual for the MIK sampling during the North Sea IBTS, which are currently being revised. All of these manuals will be submitted to ICES in their newest version until the end of 2017. Staff exchange has been a routinely performed in IBTS surveys with great success and advantage to the surveys standardization. The group strongly recommends that this practice continues and involves more countries. IBTSWG is willing to support the establishment of a WG on Marine Litter. This would facilitate improvements on collection and recording protocols, data checking procedures for the database and creation of a field guide. IBTSWG is planning to organize a flume tank workshop together with WGFTFB to identify a possible new standard survey gear for the NS-IBTS.

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