Selection of indicators for assessing and managing the impacts of bottom trawling on seabed habitats

  • Jan Geert Hiddink (Creator)
  • Michel J. Kaiser (Creator)
  • M. Sciberras (Creator)
  • Robert A. Mcconnaughey (Creator)
  • Tessa Mazor (Creator)
  • Ray Hilborn (Creator)
  • Jeremy Collie (Creator)
  • C. Roland Pitcher (Creator)
  • Ana M. Parma (Creator)
  • Petri Suuronen (Creator)
  • Adriaan Rijnsdorp (Creator)
  • Simon Jennings (Creator)



1. Bottom-trawl fisheries are the most-widespread source of anthropogenic physical disturbance to seabed habitats. Development of fisheries-, conservation- and ecosystem-based management strategies requires the selection of indicators of the impact of bottom trawling on the state of benthic biota. Many indicators have been proposed, but no rigorous test of a range of candidate indicators against 9 commonly-agreed criteria (concreteness, theoretical basis, public awareness, cost, measurement, historical data, sensitivity, responsiveness, specificity) has been performed. 2. Here, we collated data from 41 studies that compared the benthic biota in trawled areas with those in control locations (that were either not trawled or trawled infrequently), examining 7 potential indicators (numbers and biomass for individual taxa and whole communities, evenness, Shannon-Wiener diversity and species richness) to assess their performance against the set of 9 criteria. 3. The effects of trawling were stronger on whole-community numbers and biomass than for individual taxa. Species richness was also negatively affected by trawling but other measures of diversity were not. Community numbers and biomass met all criteria, taxa numbers and biomass and species richness satisfied a majority of criteria, but evenness and Shannon-Wiener diversity did not respond to trawling and only met few criteria, and hence are not suitable state indicators of the effect of bottom trawling. 4. Synthesis and application. An evaluation of each candidate indicator against a commonly agreed suite of desirable properties coupled with the outputs of our meta-analysis showed that whole-community numbers of individuals and biomass are the most suitable indicators of trawling impacts as they performed well on all criteria. Particular strengths of these indicators are that they respond strongly to trawling, relate directly to ecosystem functioning, and are straightforward to measure. Evenness and Shannon-Wiener diversity are not responsive to trawling and unsuitable for the monitoring and assessment of bottom trawl impacts.
Date made available18 Mar 2020


  • beam trawl
  • ecosystem approach to fisheries management
  • hydraulic dredge
  • otter trawl
  • scallop dredge
  • systematic review

Cite this