The relationship between reef fish community structure and environmental variables in the southern Mexican Caribbean

The reef fish community of the Mexican Caribbean and the factors governing its structure are poorly known. Using canonical correspondence analysis (CC A), the relationship between fish community species composition and abundan ce, and environmental variables was investigated at three Mexican Caribbean reefs. These reefs are separated by c. 70 km: Boca Paila, located in the n orthern Sian Ka'an Biosphere Reserve; Tampalam, in the southern portion of said reserve; and Majahual, an unprotected area near the Mexico/Belize bord er. One hundred and thirty-four fish species belonging to 41 families were identified by underwater visual census. Their quantitative data, and 15 env ironmental Variables collected during 60 sample transects, were analysed. T he sample stations were distributed among the three reefs, and covered five dominant habitat types: reef lagoon, back reef, reef crest, reef front and reef slope. The variables estimated were: temperature, depth, current dire ction, current intensity, vertical relief, visibility, topographical comple xity and substratum coverage (percent of sand, seagrass, algae, rock and ru bbles, gorgonians, massive coral, branching coral and encrusting coral). Or dination diagrams with points based on fish species, sample sites, and envi ronmental variables, showed a pattern mainly determined by degree of reef s ite complexity. Habitat scale environmental factors defined element distrib ution in three main areas: (a) reef fish species associated with lagoon and back reef sites of low topographical complexity; (b) species associated wi th intermediate complexity reef crest sites; and (c) species associated wit h high complexity reef front and reef slope sites. Nearly 52% of the variat ion in fish species data was explained by environmental variables in the di rect and simultaneous ordination analysis. Topographical complexity was the most important variable, but depth, encrusting coral coverage, and vertica l relief also had significant effect on fish species. Use of multivariate s tatistical methods proved valuable in deciphering the reef fish community s tructure patterns in the southern Mexican Caribbean. The current study prov ides a base for future reef fish research and regional tourism and fisherie s management. (C) 1998 The Fisheries Society of the British Isles.