Text A. Aquaculture water facilities

When describing aquatic production systems, the aquaculturist refers to the water-holding facility in which the organisms are grown. Several kinds of water facilities may be needed for growing fish. The kind of facility depends on the size of the farm and the type of fish farming. These facilities are grouped into 4 types: ponds, cages, raceways and recirculating systems.

1. Flow-through systems or raceways. Whenthere is an abundant and easy to harness supply of clean water a concrete raceway or earthen pond is constructed. The constant flow of water creates a favorable place to raise fish. Generally the source of water is a spring or artesian well and cold water species, such as trout, are raised. Fish waste is collected in the raceway or pond and periodically removed. Flow-through systems require a receiving stream that has adequate flow to assimilate the discharge without changing the water quality of the stream.

2. Pond systems. Pond systems are often used on sites where water supply and/or water discharge volumes are limited. Ponds require more land area and should not be constructed in wetlands. A typical use of pond systems is in growing warm water species from fry to fingerlings. The ponds are initially filled with water and fertilized to create a natural growth of aquatic organisms to provide a natural food source for the fry. With low fish densities, they can grow for a whole season with natural aeration and some supplemental feeding. Higher densities of fish may require mechanical aeration, supplemental feeding and a supplemental flow-through water source.

3. Recirculating systems. The advantage of recirculating systems is that a high density of fish can be kept at optimum temperatures by removing the fish waste and reusing the water. The rate of growth is usually faster and the system can be covered to protect the fish from predators. For sites with limited water supply, limited discharge opportunities or limited land area, recirculating systems may be the best alternative. However, technology for effective and reliable waste treatment systems to clean the water for reuse is more expensive and not totally reliable.

4. Cage systems. Cage culture of fish uses existing water resources (lakes, ponds) but encloses the fish in a cage or basket, which allows water to pass freely between the fish and the pond or lake. One of the main advantages is the ease of harvesting. Cage culture is an alternative to pond culture.