Intensive aquaculture, especially the production of carnivorous species, requires artificial feeding. Fishmeal and oil are preferred to vegetable proteins, since marine proteins provide the essential nutrients required by farmed fish. Therefore, given the stagnant production of reduction species and the rapid increase in aquaculture production, fishmeal availability would pose a biological constraint on aquaculture contribution to world fish supplies in the future, unless alternative feed sources can be incorporated in diets. In this paper, the technical substitutability between fish and vegetable based feeds are assessed through the estimation of Morishima elasticities of substitution. These are derived from a meta-analysis production function.