Abstract

Reef fish show patterns of distribution and diversity at all scales, from global to regional to local. At the largest scale diversity appears to be principally controlled by the interaction of tectonic and geomorphological events with evolutionary and dispersion processes. At a regional level, water column characteristics such as turbidity and current strength, perhaps requiring differential adaptation at the larval stage, may control species distribution patterns. At a local level, diversity is influenced by habitat characteristics such as depth, heterogeneity and complexity. Because of the vagaries of larval distribution and recruitment, the assemblages to be found at a site are quite variable, although the extent of this variation probably differs among species and areas. It is not clear that stochasticity per se promotes local or regional diversity, but the fact that currents must frequently carry larvae of a species from areas where it is a superior competitor to ones where it is an inferior competitor seems very likely to do so. But regarding the tantalising issue of the high biodiversity of reef fishes – ‘why is it that the species richness of coral reef fish assemblages is so high?’ – we have no clear answer. There are various plausible mechanisms, but as yet no conclusive evidence to indicate their relative importance. However, efforts to conserve coral reefs and coral reef fishes should not be delayed by such lack of full understanding.