Aquaculture includes a wide diversity of species raised in diverse aquatic environments that include freshwater, brackish, and marine systems (Table 1). Aquaculture products are farmed for food consumption, for sportfish-ing, for bait, for clothing (alligator skins), for pets (ornamental fish and feeders), and for industrial processes (seaweeds for agar and carrageenan). Polyculture is an appealing concept that maximizes production by stocking different species in the same pond, thus exploiting various trophic levels in a pond environment.
Aquaculture is limited by the nature of aquatic organisms and the medium of their water environment. Unlike all other domesticated livestock, fish and invertebrates are cold-blooded and require a narrow temperature range for good growth. In water, gravity is nearly overcome by the buoyancy of the medium, reducing energy expended in daily movements. Oxygen is a limiting factor because it is relatively insoluble in water. Depending on temperature and salinity, water is saturated with oxygen at 5.2 to 14.6 mg/L; in contrast, air contains approximately 21% oxygen. Water is an excellent solvent for nitrogenous wastes, which makes them difficult to concentrate and remove. In ponds, fish wastes stimulate growth of phytoplankton and bacteria that are difficult to control or concentrate for removal. Water quality in warmwater fishponds is to a large extent controlled by the plankton community.1-6-1
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