Marine Megafauna: Sea Turtles, Seabirds and Marine Mammals

Abstract

Seabirds, marine mammals and sea turtles are assembled within the Amniota group. The term non-fish vertebrates is not a taxonomically defined group, and comprise vertebrates strongly associated to the marine environment during the whole or a significant portion of their life-cycles. The biological features of each group are very different although their ecological roles and life history traits are similar. Consequently seabirds, marine mammals and sea turtles are exposed to nearly the same threats. While many organisms share their time in land and water (e.g. seabirds, sea turtles, pinnipeds), others live only in the oceans (e.g. cetaceans and sirenians). Non-fish vertebrates are distributed in all over the seas from the poles to the Equator and from shallow to deep waters. Oceans are heterogeneous environments characterized by patchy prey distribution over space and time; hence predators are concentrated in areas of high prey abundance. These hot spots are the result of physical processes, such as upwellings, eddies, gyres or sea-ice edges, and their interaction favouring productivity and prey concentration. Not only abundance can be affected by these physical drivers but also diversity (or species richness) which is particularly high in the Southern Oceans and central Pacific Ocean. This chapter is aimed to provide a broad overview of the life-history patterns of sea turtles, seabirds and marine mammals, their functional roles in their ecosystems and conservation issues that different populations are nowadays facing