Thirty-six scleractinian coral species were identified in situ during the first comprehensive quantitative survey of reefs around the Commonwealth of Dominica. Porites astreoides dominated most assemblages within the 1,146 m super(2) area examined, constituting 29.7% of the total live coral recorded (166 m super(2)). The abundance of constructional, yet non-reef-building, species along the west coast may be one of the reasons for the paucity of reef accretion. Coral reefs in the strictest sense are found along the narrow shelf of the west coast where they are sheltered from turbulence by depth and coves. Madracis mirabilis was among the main reef builders, forming mono-, as well as bi-specific banks with Porites porites. East-coast reefs were characterized by patch and fringing reefs whose main scleractinan component were built by A. palmata frameworks. However, these reefs had a comparatively low live cover (9.25%). East-coast reefs (windward) were also significantly less diverse (ANOVA, F=9.1, P=0.01) than west-coast reefs (leeward), among which shallow sites (1-5 m) were significantly less diverse (ANOVA, F=16.2, P=0.01) than deeper sites (6-18 m). A negative correlation was detected between the live cover of Scleractinia and other sessile invertebrate groups, mostly sponges, hydrocorals and zooanthids. No correlation between the presence of Scleractinia and algae was found. Given Dominica's young and narrow shelf, the assemblage types are harbored within a relatively small area suitable for reef development and lie in close proximity to the shoreline where coastal developments are the source of many disturbances. Coral reefs of Dominica can be considered as marginal systems yet a historically important artisanal fishing resource. Although it is doubtful that these reefal habitats have remained unaffected by human activities, new user groups are targeting Dominica's marine resources and thus the justification for conservation measures is suggested.
