1. MEY. When relating total revenues from fishing to total fishing effort in a surplus production model, the value of the largest positive difference between total revenues and total costs of fishing (including the coast of labour and capital) with all inputs valued at their opportunity costs. The MEY is obtained when marginal costs of fishing effort are equal to marginal revenues. It is equal to the maximum rent obtainable from the fishery.
2. The maximum (sustainable) amount of economic benefits, measured as the sum of net benefits to producers and consumers, and resource rent. Under static conditions (deterministic, no discounting), the yield for which average revenue equals long terms marginal cost. Actually a social (societal) maximum often equated with maximum rent.