7. APPLICATION OF REMOTE SENSING TO FISHERIESThe sea covers two thirds of the earth's surface. To a large extent, man is dependent on it for food species which include fish, shellfish, marine mammals, turtles, aquatic plants and algae. To exploit these resources more effectively, fishermen must catch the most fish possible (within biological constraints) while, at the same time, minimizing costs and optimizing the scheduling of their operations. Reliable environmental information is required from the scientific community for these purposes. Remote observations of the sea surface can provide a significant part of the information needed to assess and improve the potential yield of the fishing grounds. In the past, remote sensing was used predominantly to assist in the efficient harvesting of natural resources. Today it is being used for resource management, conservation and exploitation.Variations in environmental conditions affect the recruitment, distribution, abundance and availability of fishery resources. It is not possible to measure remotely the entire range of information needed to assess changes in the marine environment. Knowledge of particular conditions and processes affecting fish populations, however, may often be deduced using measurements made by remote sensors, e.g., concentration of dissolved and suspended matter, variations in primary production levels, distribution of surface isotherms, location of frontal boundaries, regions of upwelling, currents and water circulation patterns. The parameters providing information on these environmental factors may allow a forecast of fish distribution or more generally the definition of marine fish habitats. These are often easier to sense remotely than the presence of fish.Remote sensing techniques can be utilized directly, indirectly or as general aids in the detection and assessment of fishery resources.
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