Multiyear footprint of the Danish bottom-towed fisheries in the Danish EEZ for 2010-2022.
These raster layers (.tif) represents the fishing footprint of Danish bottom-towed fishing gears in the Danish Economic Exclusive Zone (EEZ). We have provided annual footprints for 2010-2022, and the multiyear footprints for the periods 2010-2016, 2017-2022, and 2010-2022, similar to to data shown in the online mapping tool, under the "multiyear footprint" page (https://doi.org/10.11583/DTU.23617944.v1). The multiyear footprints represent the cumulative fishing footprint over that period, showing how much of the seabed has been affected by physical abrasion of bottom-towed fishing gears (from Danish vessels).
Data from the Vessel Monitoring System (VMS), the Automatic Identification System (AIS), and the Black Box (BB) system were combined with electronic logbook data to determine fishing activity location. (see van der Reijden et al (2023) DOI:10.1016/j.marenvres.2023.105935 for a more detailed description). From that, overall fishing intensity was determined as the Swept Area Ratio (SAR), which should be interpreted as the number of times the raster cell is fished per year. A SAR-value lower than 1 means that the raster cell is not completely fished; a value higher than 1 means that the raster cell has been fished completely (and even more frequently) than once a year. Find more information, including a visual example of the SAR-calculation here: https://ono.dtuaqua.dk/DDFAM/ (under the tab "Information"). More information on how the multiyear footprint is determined can be found at the same location.
The fishing intensity is presented in 8 classes:
>> 0 - 0.5*
>> 0.5 - 1
>> 1 - 2
>> 2 - 5
>> 5 - 10
>> 10 - 15
>> 15 - 20
>> 20+
* grid cells with SAR values ≤ 0.05 are set to 0.
Note that we strongly advice to not fully color grid cells with the lowest fishing intensity class in footprint maps, as that will cause a visual mismatch between maps and actual footprint numbers.
The raster layers have a spatial resolution of 0.001 x 0.001 longitude x latitude degree (ca 100 x 60 m) and are saved in the ETRS89 UTM32 projection (EPSG: 25832). Note that the fishing data in this raster layer has been restricted to the Danish EEZ; it does not mean that Danish fisheries are not active in foreign waters.
