Community structure and patterns of diversity in reef fish communities in the Tropical Western Atlantic and Tropical Eastern Pacific

This thesis presents the results of a comparative study of reef fish communities on either side of the Western Isthmus of Panama (IOP). 288 visual censuses were carried out in each region. 128 fish species of 38 families were found in the Caribbean and 126 species of 44 families in the Pacific. The numbers of families and species do not differ markedly but the number of species recorded per sampling area was higher in the Pacific. Reef fishes depend on recruitment success, which is related to local oceanography and the connectivity and diversity of habitats, rather than to coral cover and diversity. Herbivores predominate in the Caribbean; planktivores and piscivores in the Pacific. Most reef fish reach larger sizes in Pacific. In both regions, the highest number of species is found in exposed rocky zones with high substrate diversity and complexity; followed by massive coral reefs. Individuals are smaller on low-complexity substrates in the Caribbean and in coral branches and holes in the Pacific, which provide refuge areas from predation and strong water movements. Better swimmers occur typically in exposed zones in Caribbean and have a wide spatial distribution in Pacific. Geminate species show strong habitat plasticity on both sides of the IOP, but retain similar habitat preferences in terms of morphology and depth regardless of the taxonomy of the benthic fauna and flora.