1. This paper describes the use of multivariate analytical techniques as an aid to classifying and assessing the nature conservation value of rocky intertidal communities round the Northern Ireland coastline.
2. Semiquantitative species abundance data from 128 rocky shore transects distributed round the coastline were subject to multivariate analysis in order to formulate a classification scheme for shore communities. Several different techniques were used on the grounds that a robust classification scheme should not be dependent upon the details of statistical methodology. Cluster analysis (three strategies) and TWINSPAN were used to produce hierarchical classification schemes, and ordination was used to assess the validity of suggested community boundaries.
3. The resulting classification scheme of rocky shore communities is presented and discussed in terms of the six scientific/ecological criteria which Mitchell (1987) identified for the comparative evaluation of marine habitats and communities for nature conservation purposes.