A survey of post-Pleistocene hydrologies and living aquatic ecologies identifies key variables which shaped fish communities in European and surrounding waters into Roman times. Provides a basic introduction to key ecological concepts such as habitats, food webs, predator–prey relations, ecological ‘guilds’, and environmental tolerances of fishes. Signs of localized negative effects of Roman consumption on especially inshore and estuarine Mediterranean fishes were, however, mostly effaced following late antique disintegration of classical cultures in the West.