ABSTRACT
Dietary nutrient requirements for major species of cultured fish, for example, channel catfish, Ictalurus puntatus; rainbow trout, Oncorhynchus mykiss; and tilapia, Oreochromis aureus, in the United States are reasonably well known (NRC 1993). Diets for these species are formulated to contain levels of essential nutrients in excess of minimum dietary requirements to account for slight differences in the essential nutrient levels of major diet in gredients, such as fish meal, and to cover any losses associated with diet manufacture and storage. Essential nutrients in fish diets are the following: (1) 10 amino acids; (2) essential fatty acids, for example, n-3 for marine fish and n-6 plus n-3 for freshwater fish; (3) 15 vitamins, including 4 fat-soluble and 11 water-soluble vitamins; and (4) about 10 minerals (Lovell 1998). Fish can obtain most minerals, except phosphorus, from both their rearing water and their diet, and although many minerals are known to be essential for growth and metabolism of fish, the need for a dietary source depends on the mineral and its concentration in the culture water (Lall 1989).
