Phosphorus (P) in marine feed ingredients provide natural high P content in commercial fish feed, but is poorly available to fish in the crystal structure with calcium (Ca) known as hydroxyapatite in fish bones. Pilot studies have shown that it is possibl e to improve the digestibility of phosphorus (P) in fish bone 2-3 fold by technological treatments (Aksnes, 2002). Activation of immobilized nutrients from fish bone represents a novel method to improve the utilisation of available marine feed resources a lready indicated to be industrially relevant and with potential large economical value. The most important raw material available for fish meal production in Norway are small size industrial fish such as blue whiting and fishery offal from the fish indust ry, both providing natural high P content. Based on alternative technological processing conditions of the bone fraction from such raw materials, the following project will aim to develop improved marine feed ingredients with high P digestibility and with predictable impacts on growth, health and welfare of intensive farmed fish. Dietary impacts of the new marine feed ingredients on digestion, absorption, tissue retention and excretion of variable P forms and solubility will be studied in Atlantic salmon and rainbow trout, and guidelines for improved and adequate nutritionally Ca: P-balanced feeds will be provided to the aquaculture industry. Efforts to improve the efficiency of P utilisation from marine feed resources and provide diets that just meet the P requirements of fish will decrease the effluent of P to the environment and ease the aquaculture industries needs to follow the new water frame directive forwarded from the EU (Dir. 2000/60/EC).