Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V14, Page 270 of the 1911 Encyclopedia Britannica.
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SOUTHERN ZONE.—The boundaries of this zone have been indicated in the description of the equatorial zone; they over-lap the southern boundaries of the latter in South Australia and South America, but we have not the means of defining the limits to which southern types extend northwards. This zone includes Tasmania, with at least a portion of south-eastern Australia (Tasmanian sub-region), New Zealand and the Auckland Islands (New Zealand sub-region), and Chile, Patagonia, Tierra del Fuego and the Falkland Islands (Fuegian sub-region). No freshwater fishes are known from Kerguelen's Land, or from islands beyond 55° S. lat. The Tropical American region is the richest (about 1300 species) ; next follow the African region (about r000), the Indian region (about 800), the Europaeo-Asiatic region (about 500), the North American region (about 400), the Tropical Pacific region (about 6o) ; whilst the Antarctic region is quite insignificant. Of the migratory fishes, or fishes travelling regularly from the sea to fresh waters, most, if not all, were derived from marine forms. The anadromous forms, annually or periodically ascending rivers for the purpose of spawning, such as several species of Acipenser, Salmo, Coregonus, Clupea (shads), and Petromyzon, are only known from the northern hemisphere, whilst the catadromous forms, spending most of their life in fresh water but resorting to the sea to breed, such as Anguilla, some species of Mugil, Galaxias and Pleuronectes, have representatives in both hemispheres. (G. A. B.)
End of Article: SOUTHERN ZONE

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