The inland fishery in South Sumatra, Indonesia, is an important source of income, employment and protein to small-scale fishers. Some overall indicators, such as virtual disappearance of certain important species and continuous reduction in the size of harvested fish, indicate that the fishery is not being exploited on a sustainable basis. In this study, an evaluation of the status of the existing fish stock is undertaken, and an analytical model for identifying efficient levels of exploitation of the fishery is developed. Primary data are used to describe the current costs of fishing effort. Secondary data, combined with results of analysis of primary data, are then used to derive a supply function for the fishery. Different types of fishing gear are standardised into a single type of fishing unit, and mixed species of harvested fish are treated as an aggregated fish stock. Empirical results reveal that both riverine and swamp fisheries in South Sumatra were biologically and economically over-fished during the period of study. This implies that regulation is required to reduce the level of fishing effort.