Accuracy of VMS data from Norwegian demersal stern trawlers for estimating trawled areas in the Barents Sea

Abstract

The accuracy of vessel monitoring system (VMS) data, used to determine fishing activity in the trawl fishery for gadoids in the Barents Sea, was studied by observer notes and Global Positioning System (GPS) data from two Norwegian vessels in October 2007. A speed rule of 2–5 knots correctly classified 75–80% of the fishing activity and 85–90% of the non-fishing activity. Linear interpolation between hourly VMS recordings underestimated trawl trajectories by 15%. The median haulwise difference between the VMS and the GPS trajectories was ∼500 m. The interpolated VMS data are appropriate for mapping the large-scale distribution of fishing effort and the area impacted, but to link fishing activities with small-scale mapping of benthos, more-frequent VMS-update times and more-refined interpolation techniques are required.