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International Committee Forms to Study Bottom-trawl Effects

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There is considerable evidence that mobile bottom-contact gears (MBCG) such as trawls and dredges affect the integrity of benthic environments that support prey and provide habitat for managed populations of fish and crab. Widespread use of these gears could thus have substantial effects on the growth, survival, and productivity of these stocks. There is, however, considerable variability in the magnitude and characteristics of the effects. Hard-bottom areas with surface-dwelling invertebrate fauna are particularly sensitive, whereas soft-bottom areas with frequent natural disturbances are relatively insensitive. Given that approximately 25% of world fish catch comes from the use of these gears, a clear understanding of the overlap between trawling effort and different benthic habitats is of considerable global importance.

An international group of experts in ecology and fisheries management has formed to summarize the global use of mobile fishing gears, their impacts on marine habitats and the productivity of fish stocks, and related management practices. The committee is comprised of individuals from both academia and government and is being lead by Professors Ray Hilborn (University of Washington, Seattle), Simon Jennings (Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, U.K.), and Michel Kaiser (Bangor University, Bangor, U.K.). Other members of the committee are Drs. Adriaan Rijnsdorp (Wageningen University and Research Center, Ijmuiden, Netherlands), Roland Pitcher (Commonwealth Scientific and Industrial Research Organization, Brisbane, Australia) , Bob McConnaughey (NOAA Alaska Fisheries Science Center, Seattle), Jeremy Collie (University of Rhode Island, Narrangansett), Jan Hiddink (Bangor University, Bangor, U.K.), and Ana Parma (Argentine Council for Science and Technology , Chubut, Argentina). Two post-doctoral research associates (Drs. Ricardo Amaroso and Kathryn Hughes) are also actively working on the project.

The full project will consist of five phases spread over the next 2 years. The first phase of this project will systematically map MBCG effort and its distribution with respect to benthic habitats. Phase 2 will compile and evaluate data about the impacts of MBCG on the abundance and diversity of biota. Phase 3 will use information from the first two phases to conduct a risk assessment of the effects of trawling and to illustrate trends in the risk of change to seabed habitats and communities. Phase 4 will look at the medium- and long-term impact of trawling on the productivity and sustainable yield of different target species and ecosystems. Phase 5 will identify and test a range of management options and industry practices that may improve the environmental performance of trawl fisheries, with a view to defining ‘best practice.’

To date, a questionnaire has been widely distributed to stakeholders and the responses were compiled to identify priority issues. The committee’s first meeting was held at the University of Washington School of Aquatic and Fishery Sciences on 17-19 June. The next meeting is tentatively scheduled for the Netherlands in November of this year. Additional details about the project and the study group are available at

By  Bob McConnaughey



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