The 'moderation process' took place in response to a requirement by the European Commission to make improvements to the list of candidate SAC sites previously submitted by the UK Government in 1997. The moderation process was able to:

- modify existing candidate SAC sites to include additional habitats and species from Annex I and II of the Habitats Directive,

- change site boundaries to better encompass existing features or to accomodate new features, and

- identifiy new SAC sites.

The Countryside Council for Wales (CCW), as the advisor on nature conservation to the National Assembly for Wales, together with the UK Joint Nature Conservation Committee, identified which existing sites should be modified and also identified additional sites for SAC designation. A list of proposed changes was submitted to the Assembly. The selection process is required by the EC to be based on scientific criteria only. Newly proposed sites are called 'possible SACs' at this point. Existing candidate sites remain as 'candidate' but are described as having 'proposed amendments' (to boundaries and/or their list of features).

On behalf of the Assembly, CCW carried out a consultation with interested parties on the scientific basis for the proposed amendments and additions. The closing date for responses was 4 December 2000. Following this, the moderated list of sites was submitted by the UK Government to the European Commission. At this stage the sites became candidate SACs.

The Pembrokeshire Marine SAC had many changes due to the moderation process. The site name change from 'Pembrokeshire Islands' to 'Pembrokeshire Marine' was the most obvious, and clearly better represents the purpose of the site's designation.

An extension to the existing candidate SAC site boundary was added to include the limestone reefs off the south Pembrokeshire coast.

Additional species (for which the site is considered to support a significant presence) included:

• Otter (Lutra lutra)
• Allis shad (Alosa alosa)
• Twaite shad (Alosa fallax)
• River lamprey (Lampetra fluviatilis)
• Sea lamprey (Petromyzon marinus)

Additional habitats (for which the site is considered to support a significant presence) included:

• Coastal lagoons
• Mudflats and sandflats not covered by sea water at low tide
• Atlantic salt meadows (Glauco-Puccinellietalia maritimae)
• Sandbanks which are slightly covered by sea water all the time
• Submerged or partially submerged sea caves

Pre-moderation the 'Pembrokeshire Islands' cSAC did not extend to cover the south Pembrokeshire coast, and only listed grey seals, reefs, shallow inlets and bays, and estuaries as it's conservation features.