Use an electric (pulse) trawl

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Three studies examined the effects of using an electric (pulse) trawl on marine fish populations. The studies were in the North Sea (Belgium, Netherlands and multiple European countries). 





  • Reduction of unwanted catch (3 studies): Two replicated, paired, controlled studies and one review in the North Sea found that using an electric/pulse trawl reduced the catches of non-target or undersized (discarded) commercial fish in some or all cases, compared to using a standard trawl.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, paired, controlled study in 2000 of an area of seabed in the North Sea, off Belgium (Polet et al. 2005) found that electric pulse trawls targeting brown shrimp Crangon crangon reduced the amount of some unwanted and undersized fish caught compared to standard trawls. Of 12 comparisons, catches of undersized commercial fish were lower in pulse trawls than in standard trawls for whiting Merlangius merlangus in four (58–69% lower), sole Solea solea in two (41–60%), plaice Pleuronectes platessa in five (40–80%) and dab Limanda limanda in two comparisons (61–65%). Lower catches in pulse trawls were also reported in non-commercial tub gurnard Trigla lucerna (one of three comparisons), pogge Agonus cataphractus (three of 12 comparisons), dragonet Callionymus spp. (two of 10 comparisons) and goby Pomatoschistus spp. (six of 12 comparisons). Catches of six other non-commercial species were similar in both trawl designs. Catches of legal-sized commercial fish were typically similar in pulse trawls and standard trawls, except for lower catches of flounder Platichthys flesus (29–37%) and dab (17%) in one and two of 12 comparisons respectively. In addition, undersized shrimp catches were reduced in 11 of 15 cases. In 2000, experimental fishing was undertaken on the Flemish Banks off the Belgian coast using two beam trawls simultaneously, a standard trawl and an experimental electric pulse trawl, with pulse generators fitted to the beam of the trawl in one of two array configurations. Fifty-seven hauls were completed with the experimental trawl being towed on one side of the vessel and the standard trawl on the other. Full details of trawl design and generator configurations are provided in the original study.

    Study and other actions tested
  2. A replicated, paired, controlled study in 2011 in an area of seabed in the North Sea, Netherlands (van Marlen et al. 2014) found that fishing for flatfish using an electric pulse trawl reduced the catches of discarded fish and undersized plaice Pleuronectes platessa and sole Solea solea compared to a conventional beam trawl. Average catch rate of all discarded fish (mainly bottom dwelling species – see paper for data for individual species/groups) was reduced by 57% in the pulse trawl (108 fish/ha) compared to the beam trawl (62 fish/ha). Fewer individuals of smaller sizes of the target species plaice and sole were caught in the pulse trawl than the beam trawl (data reported graphically). Data were collected in May 2011 from 126 trawl by three vessels fishing near each other. Two vessels used different types of pulse equipment (data pooled) and the other was a conventional tickler chain beam trawl (see original paper for specifications). Discarded catch was sampled from 33 hauls from each vessel.

    Study and other actions tested
  3. A review in 2015 of electrotrawling activity in the North Sea (Soetaert et al. 2015) found that electric pulse trawls reduced unwanted catch, but some damage occurred to fish compared to standard trawls. Unwanted catch was lower in pulse trawls in three cases (30–50% less) and catches of commercial sole were lower in one case (13–22%), compared to using tickler chains. In two cases where electric pulses were used, one in Belgium and one in the United Kingdom, catches of small unwanted sole Solea solea and other small flatfish were lower compared to standard trawls. Cod Gadus morhua, but not lesser-spotted dogfish Scyliorhinus canicula, suffered spinal fractures, other injuries and death at all sizes in one case and only at adult sizes in one case, when fish were close to electric fields (injuries 9–70%, death up to 30%). The review summarised the development of electrofishing using trawls in European waters. Controlled studies (field and laboratory) of the effects of electrofishing on fish were also reviewed.

    Study and other actions tested
Please cite as:

Taylor, N., Clarke, L.J., Alliji, K., Barrett, C., McIntyre, R., Smith, R.K., and Sutherland, W.J. (2021) Marine Fish Conservation: Global Evidence for the Effects of Selected Interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Marine Fish Conservation

This Action forms part of the Action Synopsis:

Marine Fish Conservation
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust