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  • ICES SCIENTIFIC REPORTS

    RAPPORTS SCIENTIFIQUES DU CIEM

    ICES INTERNATIONAL COUNCIL FOR THE EXPLORATION OF THE SEA CIEM CONSEIL INTERNATIONAL POUR L’EXPLORATION DE LA MER

    ICES WORKING GROUP ON ELECTRICAL TRAWLING (WGELECTRA)

    VOLUME 2 | ISSUE 37

  • 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

    The material in this report may be reused for non-commercial purposes using the recommended cita- tion. ICES may only grant usage rights of information, data, images, graphs, etc. of which it has owner- ship. 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 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.

    ISSN number: 2618-1371 I © 2020 International Council for the Exploration of the Sea

  • ICES Scientific Reports

    Volume 2 | Issue 37

    ICES WORKING GROUP ON ELECTRICAL TRAWLING (WGELECTRA)

    Recommended format for purpose of citation:

    ICES. 2020. ICES Working Group on Electrical Trawling (WGELECTRA). ICES Scientific Reports. 2:37. 108 pp. http://doi.org/10.17895/ices.pub.6006

    Editors

    Adriaan Rijnsdorp • Mattias van Opstal

    Authors

    Pim Boute • Julie Bremmer •.Clive Fox • Martin Lankheet • Pieke Molenaar • Hans Polet • Adriaan Rijnsdorp • Edward Schram • Arianna Servili • Daniel Stepputtis • Justin Tiano • Mattias van Opstal

  • ICES | WGELECTRA 2020 | I

    Contents

    i Executive summary .......................................................................................................................iii ii Expert group information ..............................................................................................................IV 1 Introduction ................................................................................................................................... 1 2 Electric fishing for razor clams....................................................................................................... 3 3 Pulse fishing for brown shrimps .................................................................................................... 4 4 Assessment Framework ................................................................................................................ 5 5 Pulse Fishery for sole ..................................................................................................................... 7

    5.1 Fishing gears .................................................................................................................... 7 5.2 Towing speed ................................................................................................................... 8 5.3 Fuel consumption ............................................................................................................ 9 5.4 Description of the electrical components and pulse stimulus ....................................... 10 5.5 Fishing effort and landings ............................................................................................. 12 5.6 Habitat association of pulse and tickler chain beam trawls .......................................... 13 5.7 Selectivity and catch efficiency ...................................................................................... 16 5.7.1 Landings and discards .................................................................................................... 16 5.7.2 Bycatch of benthos ........................................................................................................ 18 5.8 Discard survival .............................................................................................................. 19

    6 Field strength around a pulse trawl ............................................................................................ 21 6.1 Effect of salinity and temperature on field strength ..................................................... 21 6.2 Exposure to electrical disturbance ................................................................................. 23 6.3 Electric field modelling conclusions ............................................................................... 25

    7 Threshold levels to electrical pulses ............................................................................................ 26 7.1 Fish behavioural thresholds ........................................................................................... 26 7.2 Sensitivity of electroreceptive species ........................................................................... 27 7.3 Fish muscle activation thresholds .................................................................................. 28 7.4 Thresholds for spinal injuries ......................................................................................... 29

    8 Effect of pulse stimulation on marine organisms ........................................................................ 30 8.1 Introduction ................................................................................................................... 30 8.2 Laboratory experiment on the effect of pulse exposure on sandeel............................. 30 8.3 Laboratory experiment with benthic invertebrates ...................................................... 32 8.3.1 Response of benthic invertebrates to pulse exposure .................................................. 32 8.3.2 Laboratory experiment on the effects of burrowing organisms .................................... 32 8.4 Field study on injury probability in fish caught in pulse and tickler chain trawls .......... 34 8.5 Size dependence of spinal injuries in cod ...................................................................... 36 8.6 Field sampling in the track of a pulse trawler ................................................................ 37

    9 Effect of pulse trawling on benthic ecosystem functioning ........................................................ 38 9.1 Effect of electricity ......................................................................................................... 38 9.2 Effect of resuspension ................................................................................................... 38 9.3 Effect of mechanical disturbance ................................................................................... 39 9.4 Field studies of impact pulse trawls ............................................................................... 39 9.5 Field experiments on biogeochemical effects ............................................................... 40 9.6 Conclusion ...................................................................................................................... 41

    10 Scaling up the effect of pulse stimulation to the fleet ................................................................ 43 10.1 Methods ......................................................................................................................... 43 10.1.1 Spatial scale of the analysis ........................................................................................... 44 10.1.2 Cohort analysis ............................................................................................................... 44 10.1.3 Data ................................................................................................................................ 44 10.2 Results ............................................................................................................................ 45 10.2.1 Exposure ........................................................................................................................ 45 10.2.2 Impacts on fish populations ........................................................................................... 46

  • ii | ICES SCIENTIFIC REPORTS 2: 37 | ICES

    10.2.3 Impact on discarding ...................................................................................................... 48 10.2.4 Population dynamic consequences ............................................................................... 49 10.2.4.1 Cod population level impact .......................................................................................... 50 10.2.4.2 Sole population level impact.......................................................................................... 53 10.2.5 Impact on egg and larval stages ..................................................................................... 54 Pelagic eggs and larvae ................................................................................................................ 54 Demersal eggs ............................................................................................................................. 56 10.2.6 Impact on seafloor and benthic ecosystem ................................................................... 56 Footprint ...................................................................................................................................... 56 Sediment m