Surface and subsurface swept area ratio for UK fishing vessels (≥15m) in 2012
Two layers are shown:
- Surface swept area ratio for UK vessels (≥15m) in 2012 - JNCC Report 515 - figure 1 (surface abrasion) (restricted zoom)
- Subsurface swept area ratio for UK vessels (≥15m) in 2012 - JNCC Report 515 - figure 2 (subsurface abrasion) (restricted zoom)
To support a vulnerability assessment approach, JNCC are developing methods for creating geospatial pressure datasets for use at a regional and national scale. These datasets are created using a GIS to delineate their spatial extent and all activities that are known to exert the pressure are considered. In the sea one of the priority pressures on benthic habitats is Physical Damage – “Habitat structure changes - abrasion & other physical damage” referred to as ‘abrasion’, which is described as the “disturbance of sediments where there is limited or no loss of substrate from the system”.
Surface abrasion is defined as “Damage to seabed surface features” and sub-surface abrasion, defined as “Damage to seabed surface and penetration”. These definitions relate to the parts of the fishing gear that are in contact with the seabed.
Swept area was calculated per grid cell using recommended gear widths multiplied by vessel speed and the time. This was aggregated by grid cell and then divided by the area of the grid cell to determine the swept area ratio, which is the proportion of the estimated swept area to the area equivalent to each grid cell.