DOI: 10.5061/dryad.bzkh1895k
title: Selection of indicators for assessing and managing the impacts of bottom trawling on seabed habitats

description: 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.05-Mar-2020
description: Data were collated from published comparative studies of the
 effects of bottom trawling on seabed habitat and biota following a
 systematic review protocol, thereby including all available studies and
 avoiding selection bias (Hughes<i> et al.</i>, 2014). The
 methods were designed to identify and collate evidence from comparative
 control-impact studies to identify changes in state of benthic biota
 resulting from mobile bottom fishing. The searching strategy is documented
 in Hughes<i> et al.</i> (2014), which specifies the databases
 searched and search terms used in detail. Data were collated from
 published comparative studies of the effects of bottom trawling on seabed
 habitat and biota following a systematic review protocol, thereby
 including all available studies and avoiding selection bias
 (Hughes<i> et al.</i>, 2014). This dataset
 gives the resulting data collation for comparative-control impact
 studies. 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).