Frontiers in Marine Science (Nov 2015)
Fish from the Southern Ocean: biodiversity, ecology and conservation challenges
Abstract
According to the most recent census, the modern fauna of the Southern Ocean (SO) includes 374 fish species. Among them, a single group of closely related species, the suborder Notothenioidei, dominates, in terms of diversity, biomass and abundance, accounting for 115 or 30.75% of all SO species. The diversification and dominance of notothenioids in the SO is the result of a unique evolutionary history influenced by climatic and oceanographic changes that led to the isolation of the Antarctic continent and the establishment of the modern Antarctic marine environment. Taking advantage by the eradication of previous faunas, over the last 25 million years, notothenioid expanded in a variety of habitats and filled most of the available ecological niches in the frigid and isolated waters of the Antarctic continental shelf and slope. Living and functioning at subzero temperatures implied important adaptations, including freezing avoidance by antifreeze glycoproteins ( AFGPs). Among the system-wide adaptive traits holding major ecological implications, the acquisition of secondary pelagicism in some species (plesiomorphically devoid of swim-bladder) is a major. In those notothenioids, lipid deposition and reduced ossification allowed to achieve partial or full neutral buoyancy, and enabled expansion into semi-pelagic, pelagic, and cryopelagic habitats. Such an impressive ecological expansion has allowed several notothenioids to play a primary role in the Antarctic marine ecosystems. On the other side, their fine adaptation to the environment, might expose these fishes to risks that need to be properly considered and addressed. For instance, a relationship between the Antarctic silverfish (Pleuragramma antarctica), a key species in the coastal Antarctic ecosystem and the sea-ice, has recently been assessed, thus making this species potentially threatened by the ongoing climatic change, with implications for the whole ecosystem. In addition, some Antarctic fish, such as toothfishes (Dissostichus eleginoides and Dissostichus mawsoni) are primary targets of industrial fish harvesting in the SO. To increase and update the scientific knowledge on these species is mandatory in order to improve the management of Antarctic marine resources, in response to the increasing international request of exploitation. This task is presently being conducted by CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources), along with fighting the illegal, unreported and unregulated (IUU) fishing and with the establishment of MPAs (Marine Protected Areas) in various sectors of the Southern Ocean.
Keywords
