Severn Estuary/ Môr Hafren

Site overview: The Severn Estuary is the largest coastal plain estuary in the UK with extensive mudflats and sandflats, rocky shore platforms, shingle and islands. Saltmarsh fringes the coast, backed by grazing marsh with freshwater and occasional brackish ditches. This Special Area of Conservation, a type of Marine Protected Area was established to protect this special estuary. Over 100 species of fish call this area home including several rare species, such as the river lamprey, sea lamprey and twaite shad. The river and sea lamprey are a primitive type of fish having a distinctive suckered mouth but no jaws. Although numbers of lamprey have declined over the last 100 years, the UK is still one of their strongholds. They spend their adult life in the sea or estuaries but spawn and spend the juvenile phase in rivers. They use the Severn Estuary as a migratory passage to and from the sea. The Severn Estuary also has the largest eel run in Great Britain.

Designation Status
Last Updated
6 June 2017
MPA Type
Special Area of Conservation
MPA Purpose
areas which have been identified as best representing the range and variety within the European Union of habitats and (non-bird) species listed on Annexes I and II to the Directive


51° 26' 18" North,
2° 56' 41" West

Surface Area

737.69 km2
(284.82 mi.2 )


295.64 km
(183.70 mi.)

Iconic features protected by this site


  • Atlantic salt meadows (Atlantic salt meadows (Glauco-Puccinellietalia maritimae))
  • Estuaries
  • Intertidal mudflats and sandflats (Mudflats and sandflats not covered by seawater at low tide)
  • Reefs
  • Subtidal sandbanks (Sandbanks which are slightly covered by sea water all the time)


  • Sea lamprey (Petromyzon marinus)
  • Twaite shad (Alosa fallax)