The survey was carried out to describe the range of sublittoral habitats and populations of plants and animals along 70 km of the south coast of Pembrokeshire from Sheep Island at the entrance to Milford Haven to Pendine in Camarthan Bay. 45 sites were surveyed. The results are presented as descriptions of the plants and animal populations present at different locations, diagrams of the distribution of species with depth at different sites and an annotated species list. Plant and populations were found to be broadly similar from site to site although there was considerable patchiness in the occurence of many dominant or characteristic species in apparently similar habitats. Site to site differences were related mainly to the position of each site along the coast and to the rock type (limestone or sandstone). Changes in plant and animal populations along the coast and differences with the offshore Pembrokeshire islands to the west are correlated with changes which occur from west to east along the coast as: a. an increase in turbidity b. a reduction in the strength of tidal streams c. increasing shelter from wave action d. an increased amount of sediment in shallow water e. increasing variability in salinity f. increasing range in seawater temperature Nine species are recorded as of particular biographic interest or are rare species.
