Acoustic alarms reduce bycatch of harbour porpoises in Danish North Sea gillnet fisheries

  • Published source details Larsen F. & Eigaard O.R. (2014) Acoustic alarms reduce bycatch of harbour porpoises in Danish North Sea gillnet fisheries. Fisheries Research, 153, 108-112.


This study is summarised as evidence for the following.

Action Category

Use acoustic devices on fishing gear

Action Link
Marine and Freshwater Mammal Conservation
  1. Use acoustic devices on fishing gear

    A replicated, controlled study in 1997 at a wreck and an area of seabed in the North Sea, Denmark (Larsen & Eigaard 2014) found that using active acoustic devices on fishing nets resulted in fewer harbour porpoise Phocoena phocoena entanglements compared with using inactive acoustic devices or no devices. At both sites, harbour porpoises were found entangled in fewer nets with active acoustic devices attached (wreck: 0 nets; seabed: 1 net) than in nets with inactive or no acoustic devices attached (wreck: 8 nets; seabed: 15 nets). Catches of target cod Gadus morhua did not differ significantly with active, inactive, or no acoustic devices (data reported as statistical model results). Gill nets were deployed on the ocean bottom at depths of 20–80 m at two sites (a wreck and a flat/stony seabed). Nets had active acoustic devices attached (wreck: 1,052 nets; seabed: 5,596 nets), inactive (silent) acoustic devices attached (wreck: 1,056 nets; seabed: 5,210 nets) or no devices (wreck: 74 nets; seabed: 2,973 nets). Acoustic devices (prototype LU-1, Loughborough University, UK) were attached to nets at 70 m intervals and emitted 300 ms pulses at 40–120 kHz. Observers on board each of 14 fishing vessels recorded porpoise entanglements for a total of 592 hauls during 168 fishing days in August–October 1997.

    (Summarised by: Anna Berthinussen)

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