This project studied the requirements for protein and ten essential amino acids for maximizing growth and optimizing feed utilization in cultured lake whitefish. Through a series of feeding experiments, it determined the quantitative requirement for protein and limiting essential amino acids. Protein requirement was estimated with practical, fish meal-based diets.  Weight gain and tissue free amino acids were used as criteria to determine the optimum protein level for growth, which was estimated at 36.5% in the whitefish grow-out phase. Aspartate aminotransferase was characterized in whitefish as an indicator for protein metabolism. Muscle and liver lipids were characterized in whitefish that were fed experimental diets in captivity to marketable size; results indicated enriched levels of polyunsaturated fatty acids (important in human nutrition) in muscle. A broken-line model was used to establish the optimum protein level, and free amino acid concentrations in tissues were used as supporting evidence for physiologically meaningful conclusions. The optimum level of arginine and lysine in the whitefish diet is 1.2-1.5% of dry diet. Changes in free amino acids followed increased levels of these limiting amino acids.  Evidence has been presented that a dietary pH around 7.0 improves semi-purified diet utilization; however, further studies must concentrate on increased diet palatability and acceptability.  This project resulted in production of the first generation of "domesticated" lake whitefish. Further nutritional studies with domesticated whitefish will accelerate development of diets specifically formulated for this potential new aquaculture species in the Great Lakes region.