Extent of Serpulid reef and Modiolus modiolus beds in Loch Creran

The purpose of the current study was to initiate site condition monitoring of the reefs of Loch Creran. This was done to establish a baseline biological data set that would facilitate the assessment of the condition of the reef habitats in the future and to allow a judgement to be formed on the current condition of these habitats. The approach taken to achieve these objectives was to assess the extent and distribution of serpulid reefs from observations by diver along 110 transects around the loch. Detailed studies were also performed at four of the major serpulid reef sites in the loch. Here, distribution was examined with sidescan sonar, reef density by video and the community of organisms associated with the habitat by diver survey of the reefs themselves and of the surrounding sediment. The distribution and abundance of Modiolus was examined along seven relocatable transects and, at one of the major mussel beds, the size structure of the population and associated community surveyed. Subtidal rocky reefs were surveyed by diver along relocatable transects at three sites.