Eastern Atlantic region
In the eastern Atlantic Ocean, tropical shore fishes are restricted to the Gulf of Guinea, a relatively small area that extends from Dakar, Senegal, to Angola, and includes offshore islands such as the Cape Verde Islands, Annobón, and Fernando Po. Coral cover is sparse in the tropical part of the eastern Atlantic, partly due to the large amount of freshwater runoff and accompanying sediment that flows out of such rivers as the Congo, Niger, and Volta. Only a few eastern Atlantic localities have as many as four to eight genera of zooxanthellate corals, other localities having only one to three genera (Rosen 1988). The eastern Atlantic is depauperate in many fish and invertebrate groups and contains only about 500 species of shore fishes. A few families, such as the porgies (Sparidae), have radiated in the eastern Atlantic.
Comparisons among genera of shore fishes of the western Atlantic, eastern Pacific, and eastern Atlantic demonstrate the relative depauperate nature of many eastern Atlantic groups. For example, four genera that contain two to four species each in the western Atlantic and eastern Pacific have only a single species in the eastern Atlantic (Table 16.1). Such comparison of patterns of diversity among different families can tell us much about not only the zoogeography of a group but also its probable phylogenetic history, particularly if we apply modern approaches to both zoogeography and phylogeny.