Assessing Seabed Status in 24 Trawled Regions of the World

Abstract

Bottom-trawl fishing is widely considered to pose serious risks to seabed habitats. We apply a new method, suitable for datapoor fisheries, to quantify the relative benthic status (RBS) of the seabed: the amount of biota present, in equilibrium with trawl depletion, as a proportion of biota present without trawling. Estimating RBS for grid cells requires parameters for trawl impact and recovery rates, and maps of trawling intensity and habitats. Regional status is summarized by the average and cumulative distribution of grid-cell RBS values. Average RBS was >0.9 for 16 regions (i.e. trawling has depleted regional biota by <0.1) whereas three (European) regions had average RBS <0.7. Where trawl target species were managed within accepted sustainability limits (F0.9; thus, sustainable fisheries production and sustaining the environment are complementary and achievable. Within the five Australian regions, subsequent definition of 217 meso-scale eco-regions showed most had little or no exposure to trawling, but several have high trawl exposure and are priorities for future detailed habitat risk assessment. These results provide sea-scape scale indicators needed for balancing production and environmental sustainability objectives and for development of best practices for ecosystem-based fishery management, reporting and certification.