ABSTRACT
INTRODUCTION Aquacultural production of various fish and crustacean species has developed into major industries in many countries, and further development is expected as the demand for fisheries products continues to increase and supply from natural sources becomes more limited. As in more traditional forms of animal production, nutrition plays a critical role in intensive aquaculture because it influences not only production costs but also fish growth, health and waste generation. Development of nutritious and cost-effective diets is dependent on knowing a species' nutritional requirements and meeting those requirements with balanced diet formulations and appropriate feeding practices (Gatlin, 2002). Information concerning the nutritional requirements of cultured fishes has increased rapidly over the last decade as a result of heightened research efforts to support aquacultural production of established and
ENERGY YIELDING NUTRIENTS Proteins and Amino Acids
and Post, 1975) as well as caudal fin erosion, cataracts and short gill opercula (Poston and Rumsey, 1983). Methionine is another indispensable amino acid which has been reported to cause bilateral cataracts in the eye lens of some fish species such as rainbow trout (Walton etal, 1982; Rumsey et al, 1983; Poston, 1986; Cowey et al., 1992), Arctic char Salvelinus alpinus (Simmons et al, 1999) and hybrid striped bass Morone chysops x M. saxatilis (Keembiyehetty and Gatlin, 1993). However, cataracts have not been consistently observed in all fish species suffering from a deficiency in total sulfur amino acids (NRC, 1993).
