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

HIDDINK, JAN GEERT; MCCONNAUGHEY, ROBERT A; COLLIE, JEREMY S; SUURONEN, PETRI; SCIBERRAS, M.; HILBORN, RAY; KAISER, M.; PARMA, ANA M; MAZOR, TESSA; JENNINGS, SIMON; PITCHER, C. ROLAND; RIJNSDORP, ADRIAAN D

Congreso; ICES Annual Science Conference 2019; 2019

ICES

Fisheries using bottom-trawls are the most-widespreadsource of anthropogenic physical disturbance to seabed habitats. Development offisheries, conservation and ecosystem-based management strategies requires theselection of indicators of the impact of bottom trawling on the state ofbenthic biota. Many indicators have been proposed, but no rigorous test of arange of candidate indicators against commonly-agreed criteria (concreteness,theoretical basis, public awareness, cost, measurement, historical data,sensitivity, responsiveness, specificity) has been carried out. Here, wecollated data from 41 studies that compared the benthic invertebratecommunities in trawled areas with those in control locations (that were eithernot trawled or trawled infrequently), examining numbers and biomass for bothindividual taxa and whole communities, Evenness, Shannon-Wiener diversity andspecies richness and assess the performance of each against the criteria. Theeffects of trawling were stronger on whole-community numbers and biomass thanfor individual taxa. Species richness was also negatively affected by trawlingbut other measures of diversity were not. Community numbers and biomass met allindicator criteria, taxa numbers and biomass and species richness met amajority of criteria, but Evenness and the Shannon-Wiener diversity did notrespond to trawling and only met one criteria, and hence are not suitable stateindicators for monitoring the effect of bottom trawling. In conclusion,community numbers of individuals and biomass are the most suitable indicatorsof trawling impacts as they performed well on all criteria. Particularstrengths are that they respond strongly to trawling, relate directly to ecosystemfunctioning, and are straightforward to measure.