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Effects of Trawling and Dredging on Seafloor Habitat
involving fishermen and scientists. Topics for future research include the following:
identification of the forces produced by fishing gear on the seafloor and the threshold forces that injure and dislodge a range of benthic organisms;
use of various empirical approaches, such as sidescan sonar, to assess the spatial extent and overlap of trawl and dredge effects in conjunction with higher resolution effort reporting data;
development of fishing gear to reduce damage to habitat and to meet other conservation goals such as bycatch reduction and maintenance of biological communities; and
investigation of why some areas appear to continue to produce fish despite chronic disturbance by fishing gear.
Habitat disturbance has been studied mainly at small spatial scales with short-term observations of acute disturbance. Development of a landscape-scale perspective of the effects of trawling and dredging on the seabed will require a long-term commitment to higher resolution mapping of the continental shelf and slopes. Because most studies have focused on animal communities, more studies are needed on ecosystem processes (e.g., productivity, nutrient regeneration). Topics for future research include the following:
the rates and magnitude of sediment resuspension, nutrient regeneration, and responses of the plankton community in relation to gear-induced disturbance;
the dose-response relationship as a function of gear, recovery time, and habitat type to evaluate effects of repeated disturbance by fishing gear;
recovery dynamics, with consideration given to estimating large-scale effects at current fishing intensities;
acute and chronic effects of trawling in deeper water (>100 m);
recovery rates in stable and structurally complex habitats;
relative magnitude of different sources of bottom habitat disturbance;
long-term trend data for benthic production versus fisheries production; and
the effects of habitat fragmentation on total production.
Constructive interactions among stakeholders and policymakers can be facilitated through user group funding of research and through collaborative research that involves scientists and fishermen. Increased participation also will support cooperative development of alternative gears and practices. Comparative risk assessment can be used to identify priorities for acquiring quantitative data to improve risk analysis. Monitoring and evaluation of the consequences of existing management measures (e.g., gear restrictions, area closures, effort reductions) should be used to support the development of new management plans, especially in understudied regions. Aggregation and analysis of existing information on habitats, fishing effort, and efficacy of various management measures will help the regional fishery management councils meet their mandate to protect EFH. Topics for future research include the following:
develop testable hypotheses of how biological communities in different habitat types respond to fishing;
establish baselines for characteristic habitats and regions to document the effects of various fishery practices;
design quantitative models to predict fishing effects in areas that have not been studied;
validate the use of frequency-dependent distribution approaches for designating EFH and HAPC through analysis of community structure and life history parameters; and
collect and analyze data on the social and economic characteristics of trawl, dredge, and nonmobile gear fisheries to assess the tradeoffs among various management alternatives.