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  • Roland Pitcher
    CSIRO Oceans and Atmosphere, Brisbane
  • Nick Ellis
    CSIRO Oceans and Atmosphere, Brisbane
  • Simon Jennings
    4Centre for the Environment, Fisheries and Aquaculture Science, LowestoftUniversity of East Anglia
  • Jan Hiddink
  • Michel Kaiser
  • Mervi Kangas
    Western Australian Fisheries and Marine Research Laboratories
  • Robert McConnaughey
    NOAA, Alaska Fisheries Science Center, Seattle
  • Ana Parma
    Centro Nacional Patagónico, Puerto Madryn Chubut
  • Adriaan Rijnsdorp
    IMARES Wageningen UR
  • Petri Suuronen
    FAO Fisheries and Aquaculture Department, Rome, Italy
  • Jeremy Collie
    University of Rhode Island
  • Ricardo Amoroso
    University of Washington, Seattle, WA
  • Kathryn Hughes
  • R. Hilborn
    University of Washington, Seattle, WA
1. Impacts of bottom fishing, particularly trawling and dredging, on seabed (benthic) habitats are commonly perceived to pose serious environmental risks. Quantitative ecological risk assessment can be used to evaluate actual risks and to help guide the choice of management measures needed to meet sustainability objectives. 2. We develop and apply a quantitative method for assessing the risks to benthic habitats by towed bottom-fishing gears. The method is based on a simple equation for relative benthic status (RBS), derived by solving the logistic population growth equation for the equilibrium state. Estimating RBS requires only maps of fishing intensity and habitat type — and parameters for impact and recovery rates, which may be taken from meta-analyses of multiple experimental studies of towed-gear impacts. The aggregate status of habitats in an assessed region is indicated by the distribution of RBS values for the region. The application of RBS is illustrated for a tropical shrimp-trawl fishery. 3. The status of trawled habitats and their RBS value depend on impact rate (depletion per trawl), recovery rate and exposure to trawling. In the shrimp-trawl fishery region, gravel habitat was most sensitive, and though less exposed than sand or muddy-sand, was most affected overall (regional RBS=91% relative to un-trawled RBS=100%). Muddy-sand was less sensitive, and though relatively most exposed, was less affected overall (RBS=95%). Sand was most heavily trawled but least sensitive and least affected overall (RBS=98%). Region-wide, >94% of habitat area had >80% RBS because most trawling and impacts were confined to small areas. RBS was also applied to the region's benthic invertebrate communities with similar results. 4. Conclusions. Unlike qualitative or categorical trait-based risk assessments, the RBS method provides a quantitative estimate of status relative to an unimpacted baseline, with minimal requirements for input data. It could be applied to bottom-contact fisheries worldwide, including situations where detailed data on characteristics of seabed habitats, or the abundance of seabed fauna are not available. The approach supports assessment against sustainability criteria and evaluation of alternative management strategies (e.g. closed areas, effort management, gear modifications).
Original languageEnglish
Pages (from-to)472-780
JournalMethods in Ecology and Evolution
Volume8
Issue number4
Early online date11 Nov 2016
DOIs
Publication statusPublished - Apr 2017

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