Detailed mapping of fishing effort and landings by coupling fishing logbooks with satellite-recorded vessel geo-location

Individual tracking of commercial fishing vessels from vessel monitoring systems (VMS) is now widely available across Europe for scientific purposes. This enables analyses of the spatial and temporal distribution of disaggregated fishing activity as well as high resolution determination of the consequent relative fishing pressure on stocks, provided that an accurate method can link these data with the declaration of catches (logbooks). In the present study, logbook analyses to allocate the fishing activity due to various fisheries (fleet segments) are integrated with processing of raw satellite-recorded data for identifying trips at sea and fishing sequences. Both data sources are linked into one output dataset. A robust method is developed to allocate logbook catches to VMS positions, with focus on potential mismatch. The method is applied to data on the Danish Skagerrak-Kattegat fishing fleets from 2005 to 2008, where 52-56% of the VMS total effort perfectly matched (representing approximately 80% of landings); 14-18% partially matched: and 30% failed to match the logbook data, which was partially related to fleet type, area and year. Comparison of three methods for generating high resolution determination of grid-based fishing effort demonstrated only minor differences, suggesting a mainly equal dispatch of landings between each of the merged fishing positions. Despite possibly poor matching success for this particular region, we demonstrate that the approach can cope with the potentially large sources of error in the data, including the current low accuracy of available VMS pre-processing algorithms and the possible misreporting of areas and catch dates in fishermen's logbook declarations. (C) 2010 Elsevier B.V. All rights reserved.