Harbour porpoise Special Area of Conservation seasonal areas 2019

Abstract

This resource contains shapefiles showing the seasonal components for harbour porpoise Special Areas of Conservation (SACs). The seasonal components for each site reflect the areas and seasons during which harbour porpoise densities are persistently higher. These seasons are relevant with regards to management of human activity.

Three of the sites designated solely for harbour porpoise have only a single seasonal component - either summer or winter which covers the entirety of the SAC boundary (Bristol Channel Approaches; North Anglesey Marine; North Channel). The other two sites (Southern North Sea; West Wales Marine) have both summer and winter components of varying size reflecting changes in usage and distribution with the season. The harbour porpoise sites not included in this shapefile, namely Skerries and causeway and Inner Hebrides and the Minches, are sites showing consistent year-round use. The boundaries from these sites can be obtained from our SACs with marine components dataset

The site boundaries were initially drawn up in the British National Grid (BNG) projection in the Secretary of State waters and in Irish National Grid in Northern Ireland waters. Mean Low Water Springs (MLW) was used to delineate the coastal boundary. The MLW shape files were provided by the SNCBs in OSGB36 – British National Grid.

Due to the size and distribution of the proposed sites, an equal area projection was required. European Albers Equal Area Conic (AEAC_UKCS) was used with adjusted standard parallels for the UK Continental Shelf (50.2°N and 61.2°N), which minimises distortion for all sites that span the North-South extent of the UK Continental shelf (47.4 N to approximately 64 N). The transformations used to change projection from BNG to AEAC _UKCS were OSGB _1936 _To _WGS _1984 _Petroleum (appropriate for boundaries which extend 10 km from the coast) and ED _1950 _To _WGS _1984 _18 (appropriate for the modified Albers applied).