Assessing seabed status in 24 trawled regions of the world

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

Congreso; ICES Annual Science Conference 2019; 2019

ICES

Bottom-trawlfishing is widely considered to pose serious risks to seabed habitats. We applya new method, suitable for data-poor fisheries, to quantify the relativebenthic status (RBS) of the seabed: the amount of biota present, in equilibriumwith trawl depletion, as a proportion of biota present without trawling.Estimating RBS for grid cells across a region requires parameters for trawlimpact and recovery rates, and maps of trawling intensity and habitats. Regionalstatus is summarized by the cumulative distribution and average of grid-cellRBS values. Average RBS was >0.9 for 16 regions (i.e. trawling has reduced regionalbiota by <0.1) whereas three (European) regions had average RBS <0.7.Where trawl target species were managed within accepted sustainability limits(F<Fmsy), there was 93.3% probability that regional mean RBS was >0.9;thus, sustainable fisheries production and sustaining the environment arecomplementary and achievable. RBS provides a powerful seascape-scale indicator ofseabed status needed to assess sustainability risk at any threshold of status thatmay be considered appropriate for any defined habitats or region. However,sustainability thresholds and limit reference points for seabed habitats are embryonicand require further development. RBS can also be used to evaluate theenvironmental benefits of alternative management measures that may be proposedto mitigate risk from trawling (e.g. gear modifications, effort reductions,closed areas). Such evaluations would facilitate decisions regarding trade-offsbetween production and environmental objectives and development of bestpractices for ecosystem-based fishery management, reporting and certification.