Publication Abstract

Estimating high resolution trawl fishing effort from satellite-based Vessel Monitoring System (VMS) data

C.M. Mills, S.E. Townsend, S. Jennings, P.D. Eastwood and C.A. Houghton

High resolution estimates of trawling effort are needed to underpin studies of trawling impacts on species, habitats and ecosystem processes, and to monitor responses to area closure and other management actions. Satellite-based Vessel Monitoring Systems (VMS) were designed for fishery control and enforcement, but provide a potentially valuable source information on spatial and temporal patterns of trawling activity at multiple scales. Based on an analysis of VMS data for UK beam trawlers in the North Sea, we describe a method for identifying trawling activity and estimating fishing intensity based on the minimum and maximum potential spatial extent of trawling effort from VMS data. The optimal method for identifying trawling and steaming behaviour combined speed and directionality rules and correctly identified trawling and steaming in 99% and 95% of cases respectively. Using speed and directionality filtered VMS data, trawling effort was reported as area impacted per unit time per unit area at a range of grid scales from 1 to 100 km (10,000 km²). Trawling effort was found to be accurately represented at a grid cell resolution of 3 km or less. 

Reference

C.M.Mills, S.E. Townsend, S. Jennings, P.D. Eastwood and C.A. Houghton (2007) Estimating high resolution trawl fishing effort from satellite-based Vessel Monitoring System (VMS) data.  ICES Journal of Marine Science, 64: 248-255