Use a midwater/semi-pelagic trawl instead of bottom/demersal trawl

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study examined the effects of using a semi-pelagic trawl instead of a demersal trawl on subtidal benthic invertebrates. The study was in the Indian Ocean (Australia).




  • Overall abundance (1 study): One replicated, controlled, study in the Indian Ocean found that fishing with a semi-pelagic trawl did not reduce the abundance of large sessile invertebrates, which was similar to non-trawled plots, but a demersal trawl did.


  • Commercial catch abundance (1 study): One replicated, controlled, study in the Indian Ocean found that fishing with a semi-pelagic trawl reduced the abundance of retained commercially targeted fish compared to fishing with a demersal 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, controlled study (date of study unspecified) in six seabed plots in the Indian Ocean, north-western Australia (Moran  & Stephersn 2000) found that fishing with a semi-pelagic trawl did not reduce invertebrate abundance to the extent that fishing with a standard demersal trawl did. Following fishing with a semi-pelagic trawl, abundance of large sessile invertebrates (>20 cm) did not change and was similar to non-trawled plots, whereas following each fishing event with a demersal trawl their abundance was reduced by approximately 16% (data presented on a logarithm scale). The semi-pelagic trawl caught fewer commercially targeted fish than the demersal trawl. Two types of otter trawls were tested; a semi-pelagic trawl, deployed approximately 15 cm above the seabed (no contact), and a standard demersal trawl towed along the seabed (in contact). An area of seabed at 50–55 m depth that had never been trawled was divided into six 360 x 925 m plots: two plots/gear type and two non-trawled plots. Each trawled plot was trawled four times. Invertebrates attached to the seabed (>20 cm, reported as being mostly sponges, soft corals, and gorgonians) were counted from video camera recordings before and after each fishing event in trawled and non-trawled plots.

    Study and other actions tested
Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K. & Sutherland, W.J. (2020) Subtidal Benthic Invertebrate Conservation. Pages 635-732 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Subtidal Benthic Invertebrate Conservation

This Action forms part of the Action Synopsis:

Subtidal Benthic Invertebrate Conservation
Subtidal Benthic Invertebrate Conservation

Subtidal Benthic Invertebrate Conservation - Published 2020

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