Optimising the amino acid supply in tune with the requirements and improving protein utilization for body protein growth with limited impacts on the environment in terms of nutrient loads is a generic imperative in all animal production systems. With the continued high annual growth rate reported for global aquaculture, our commitments should be to make sure that this growth is indeed reflected in provision of protein of high biological value for humans. The limited availability of fish meal has led to some concerted efforts in fish meal replacement, analysing all possible physiological or metabolic consequences. The rising costs of plant feedstuffs make it necessary to strengthen our basic knowledge on amino acid availability and utilization. Regulation of muscle protein accretion has great significance with strong practical implications. In fish, despite low muscle protein synthesis rates, the efficiency of protein deposition appears to be high. Exploratory studies on amino acid flux, inter-organ distribution and particularly of muscle protein synthesis, growth and degradation and the underlying mechanisms as affected by dietary factors are warranted. Research on specific si