In 1985, T.W. Gallant published an influential essay on the potential productivity of fishing in the ancient world. He concluded that: ”the role of fishing in the diet and economy would have been, on the whole, subordinate and supplementary…” His methodological approach was original in using modern fishery data to estimate the productivity of ancient fisheries. Unfortunately his work suffered from several severe misunderstandings about ecosystems, the nature of a fishery and its biological interaction with its environment. The purpose of this paper is to discuss the statistical background for Gallant’s conclusions about fishery and the usefulness of modern catch data for historical fishery research. In order to do so, the author adopts the viewpoint of marine-environmental history, with some reference to other authors’ work on ancient fisheries.