Comparisons between tropical and temperate estuarine ichthyofaunas of western Africa and eastern South America

Abstract

This review examines the probable fish colonization processes that occurred when plate tectonics and continental drift created the South Atlantic Ocean between Africa and South America, beginning in the Late Jurassic and gaining considerable momentum during the Cretaceous. Initial fish colonization is likely to have occurred by tropical fish families utilizing the western Tethys Sea arm around North Africa to gain access to the growing epicontinental seaways and coastal zones between Africa and South America. Speciation by some of these taxa would then have occurred such that the southern temperate waters on both continents became occupied by a less species rich cool-water ichthyofauna. The current numerical family status for African and South American tropical estuarine ecoregions is 55 and 63 respectively, whereas the numerical status for temperate ecoregions is 32 and 36 respectively. A Bray-Curtis similarity matrix was created for both fish families and species from the selected tropical and temperate ecoregions. These cluster analyses showed that fish families on either side of the Atlantic were similar but that the species were not. Only a very limited number of mainly large teleosts (e.g. Megalops atlanticus) and elasmobranchs (e.g. Carcharinus leucas) occur on both sides of the Atlantic. The current large crossing distances of >3000 km for most tropical coastlines, and >6000 km for some of the temperate coastlines, restrict fish species transfers across this large oceanic basin.