Trawl Gear Behavior and Seafloor Interaction in Icelandic Waters: Coupling Gear Data with Sediment Types to Assess Trawl Impact

Abstract

Bottom-contact fishing gear, such as otter trawls, disturb the seabed much like a plow turning over soil resuspending sediment and altering the structure of the seafloor. While trawling intensity has increased globally, the mechanics driving seabed impact and their ecological implications remain underexplored. This study integrates three complementary components hydrodynamics, geotechnical properties, and operational metrics to assess seabed impacts during bottom trawling. Hydrodynamic forces acting on gear components are analyzed using otter door specifications, sediment resistance is quantified through average grain size calculations derived from 1,850 grab samples provided by the Icelandic Marine and Freshwater Research Institute (MFRI), and operational metrics such as warp tension, vessel speed, and tow depth are obtained from the Optigear system installed on the Icelandic bottom trawler Akurey. Findings show coarser sediments improved effective otter door contact area, while certain warp angles tend to cluster between similar speeds and depths. By combining real-world trawling data with refined sediment mapping techniques, this study moves beyond gear efficiency assessments to capture the physical interactions between trawl gear and the seabed. The results offer a more complete picture of sediment mobilization, providing insights critical for refining vulnerability maps and long-term seabed impact models. These findings can support more sustainable trawling strategies and inform global fisheries management, especially as seafloor integrity and oceanic carbon stores gain increasing prominence in international climate and sustainable fisheries management.