Predictability of fish assemblages on artificial and natural reefs in Barbados

Fish assemblages on four large (100 m²) artificial reefs were censused in May, June and July, 1986 and again in May 1988. The mean coefficient of variation of species' relative density decreased from 1986 to 1988, while the mean percent similarity of fish assemblages increased from 1986 to 1988. Fish assemblages on two of the large artificial reefs and on equal areas of the nearest natural coral reef were censused biweekly for 12 mo. Neither reef type (artificial or natural) nor reef location appeared to have an effect on assemblage structure. Fish assemblages on six small (1 m²) concrete block reefs were censused biweekly for 12 mo; three of the six reefs were denuded at 3-mo intervals. Assemblages on these small reefs were less predictable than those on the large artificial and natural reefs. Predictability of fish assemblages on large and small reefs generally increased with number of species present, but was not consistently related to total number of individuals present. Values of assemblage similarity varied from agreement with Australian studies, which generally espouse recruitment-limited, non-equilibrial assemblage structure, to agreement with other Caribbean studies, which generally espouse stable, resource-limited assemblage structure. It is concluded that the dichotomy of results between Australian and Caribbean studies of reef fish assemblage structure is primarily a result of different sampling methodology and analysis coupled with different species pools, and requires no difference in biological mechanism.