ICES REPORT WGELECTRA Reports/Expert Group Report/EOSG/2018...آ  ICES REPORT WGELECTRA 2018 ICES CM

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  • ICES REPORT WGELECTRA 2018

    ICES CM 2018/EOSG: 10

    REF ACOM AND SCICOM

    Report of the Working Group on Electric Trawling (WGELECTRA)

    17 - 19 April 2018

    IJmuiden, the Netherlands

  • International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer H. C. Andersens Boulevard 44–46 DK-1553 Copenhagen V Denmark Telephone (+45) 33 38 67 00 Telefax (+45) 33 93 42 15 www.ices.dk info@ices.dk

    Recommended format for purposes of citation:

    ICES. 2018. Report of the Working Group on Electric Trawling (WGELECTRA). ICES Report WGELECTRA 2018 17 - 19 April 2018. IJmuiden, the Netherlands. 155pp.

    The material in this report may be reused using the recommended citation. ICES may only grant usage rights of information, data, images, graphs, etc. of which it has ownership. For other third-party material cited in this report, you must contact the original copyright holder for permission. For citation of datasets or use of data to be included in other databases, please refer to the latest ICES data policy on the ICES website. All extracts must be acknowledged. For other reproduction requests please contact the General Secretary.

    This document is the product of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the view of the Council.

    © 2018 International Council for the Exploration of the Sea

  • Report of the Working Group on Electric Trawling (WGELECTRA)

    Contents

    Executive summary ................................................................................................................ 7

    1 Administrative details .................................................................................................. 1

    2 Terms of Reference ........................................................................................................ 2

    3 Introduction .................................................................................................................... 3

    4 Assessment framework ................................................................................................. 5

    5 Electrofishing .................................................................................................................. 7

    5.1 Introduction .......................................................................................................... 7

    5.2 Pulse trawling in the North Sea ......................................................................... 7 The number and distribution of pulse trawls in the North Sea ......... 7

    5.3 Pulse trawls used in the fishery for sole ........................................................... 9

    5.4 Field strength measurements of the sole pulse ............................................. 13

    6 Sustainable exploitation ............................................................................................. 16

    6.1 Introduction ........................................................................................................ 16

    6.2 Evolution of pulse trawl effort ......................................................................... 16

    6.3 Changes in towing speed.................................................................................. 18

    6.4 Spatial distribution of the pulse and beam trawl fishery ............................. 19 6.5 Catch rate and species composition of discards ............................................ 24

    6.6 Catch efficiency for target species sole and plaice ........................................ 26 Conclusion ............................................................................................... 27

    6.7 Species and size selectivity ............................................................................... 27 Conclusion ............................................................................................... 31

    6.8 Cod-end selectivity ............................................................................................ 31 Conclusion ............................................................................................... 32

    6.9 Survival of fish caught in pulse and beam trawl fishery.............................. 32 Conclusion ............................................................................................... 33

    6.10 Competition between fishers using pulse trawls with those using other gear ............................................................................................................ 33

    Conclusion ............................................................................................... 33

    6.11 Discussion ........................................................................................................... 34

    7 Repetitive exposure ..................................................................................................... 35

    7.1 Introduction ........................................................................................................ 35

    7.2 Frequency of exposure ...................................................................................... 35

    7.3 Repetitive exposure: theoretical approach ..................................................... 36 Time interval between trawling events ............................................... 36

  • 4 | ICES Report WGELECTRA 2018 17 - 19 April 2018

    7.4 Empirical approach ........................................................................................... 37 Methods ................................................................................................... 37 Results ...................................................................................................... 37

    7.5 Discussion ........................................................................................................... 38

    8 Target and non-target species .................................................................................... 40

    8.1 Damage due to mechanical impact ................................................................. 40

    8.2 Damage due to electrical stimulation (fractures, mortality) ........................ 41 Field samples pulse vessels ................................................................... 41 Laboratory experiments with sole pulse exposure ............................ 43

    8.3 Behaviour ............................................................................................................ 44 8.4 Reproduction ...................................................................................................... 45

    8.5 Effect of chronic exposure to sub lethal effects .............................................. 46

    9 Mechanical disturbances of sea bed ......................................................................... 47

    9.1 Penetration in sea bed ....................................................................................... 47

    9.2 Conclusion .......................................................................................................... 48

    10 Structure and functioning of the benthic ecosystem ............................................. 49

    10.1 Effects of mechanical disturbance on biomass and community composition ........................................................................................................ 49

    10.2 Bio-geochemistry ............................................................................................... 50 Field experiments ................................................................................... 51 Ex-situ exposure experiments ............................................................... 51 Sub-lethal impacts on ecosystem functioning .................................... 51 Effects from electrolysis ......................................................................... 51 Discussion ................................................................................................ 52

    10.3 Conclusion .......................................................................................................... 52

    11 Comparing ecosystem impacts of using pulse trawls or traditional beam trawls in exploiting North Sea sole .......................................................................... 53

    11.1 Sustainable exploitation of the target species ................................................ 53 Catch efficiency and Species selectivity (landings) ........................... 53 Size selectivity sole and plaice .............................................................. 53 Discards ................................................................................................... 53 Bycatch invertebrates ............................................................................. 53 Discard survival ...................................................................................... 54 Risk of overfishing ................................................................................. 54 Fishing effort ........................................................................................... 54 Spatial distribution ................................................................................. 54

    11.2 Adverse effects pulse stimulus on target and non-target teleost and Elasmobranch fish species that are exposed to the gear but not retained