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DocumentSurvey of resources in the Indian Ocean and Indonesian area 1971
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No results found.The resources of the tropical ocean derive from a number of separate ecosystems; for the present purpose there are five: the upwelling areas, offshore oceanic areas, coral seas, mangrove swamps, and coastal areas outside upwelling regions; Studies of the oceanic system lead to the conclusion that stocks of the four most valued tunas (yellowfin, bigeye, albacore, and southern bluefin) are fully exploited; other tunas and tuna-like fishes perhaps can be exploited: Spanish mackerel and especially s kipjack, whose estimated production is 100.000 tons; Coral seas are difficult to exploit, but production is likely to be high; there may be tertiary resources of Sardinella or mackerels over the whole coral area; Mangrove swamps are extensive, and their high productivity could be exploited with a variety of fish, shellfish, and crustacean cultures; the swamps need to be investigated for present resources; Upwelling areas and the associated offshore divergences are the most productive; the most p romising area for development is that off Northern Somalia and Southern Arabia, followed by the Malabar Coast and the Indonesian area. A fisheries survey should be mounted to catalogue resources of the three promising areas; surveys of pelagic resources with echo-sounders and purse-seines should be initiated all over the region but particularly in the upwelling areas. -
No Thumbnail AvailableBook (series)River Fisheries 1985
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Rivers drain all but the most arid areas of the earth through channels that are regu- lated by physical laws that impose on them certain forms. The ideal form is rarely encountered in practice and represents an end point to which geographic process tend. In general a river may be divided into two principal zones, the steep and fast flowing rhithron upstream and the sluggish and flat potamon downstream. While conditions in an individual system are highly variable along its length, similar reaches of different rivers differ much less even between continents and at different latitudes. All continents have a series of major river systems which consist not only of the river channels but also the swamps, lakes and seasonally flooded lands associated with them. Most rivers are highly conditioned by the patterns of precipitation in their basins. Differences in rainfall intensity throughout the year generate a flood wave that progresses downstream in the majority of rivers (flood rivers), al though singular geographic circumstances may distribute discharge more evenly throughout the year in some systems (reservoir rivers). The number of reservoir rivers is increasing through flow regulation and dam building. Although the basic nature of the river is determined by the rocks over which it flows, the flood regime seasonally modifies the physical and chemical conditions within the river particularly in the tropics. In higher latitudes other features of climate, such as insolation or air temperature exert an increasing influence.
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