ABSTRACT
Aquaculture includes the cultivation of aquatic organisms such as fish, shellfish, crustaceans, and plants using methods that increase the yield to a level above that naturally found in the environment. Natural aquatic ecosystems are sun-based systems with relatively long food chains meshed in complicated food web. In contrast to natural aquatic ecosystems, highly intensive artificial aquaculture ecosystems are characterized by high inputs of energy and of seed, short food chains with low energy losses, and high yields per unit area. Natural food organisms, often generated within the cultural unit, sustain the system, although there may be occasional input of fertilizer, manures, or feedstuffs. The various levels of aquaculture progress from minimal to maximal inputs of external energy, ecosystem manipulation, and management. Extensive aquaculture involves a low degree of control over the environment, nutrition, predators, competition, and disease agents. Intensive aquaculture involves a high degree of control over the system, a high level of technology, and high production levels.
