A brief but thorough discussion of potential fish protein concentrate (FPC) and projections of its future harvest, accompanied by several illustrative tables. FDC ideally is that product resulting from modern technologies which has been transformed into a stable, dry, high amino acid quality, non-toxic, water-soluble, powdery, functional substance of varied use in formulated food products. It is likely that a marine resource will be a suitable raw material for commercial FPC. The ability of the aquatic environment to provide FPC will depend greatly on two classes of under-utilized resources. One is those resources without a market because of local food preferences, dietary habits, religious prescriptions, or competition by more valuable species. The other class are those known to occur in very substantial amounts but which now are not used frequently or at all for various technological or economic reasons. It is this latter group with which this report is more concerned. Alternative, (to marine resources) high quality protein supplies also are examined. In summary, on the lower level including present meal fisheries as potential supplies of FPC and future stocks of thread herring, mackerel, etc., potentials are about 50 million metric tons. On the immediate level which includes krill, and added 90 million metric tons for a total of about 140 million metric tons potentially are available. On the high level, perhaps part of the squid catch to a total of about 10% of production or 10 million metric tons as a maximum is available, and of the lantern fishes, quantities termed "vast" are available but under present or foreseeable harvesting and processing conditions, these quantities are of little practical importance for FPC manufacture.