Among users of the water resource are fishes and fishermen. Given the importance of fisheries in the Lower Mekong River Basin, water management schemes must take the fish resource into consideration. Therefore hydrological modelling must encompass hydrobiological issues of critical importance for fisheries. This presentation is an overview of the practical aspects of modelling the relationship between water flow and fish production. The different ways of addressing this issue are listed, together with their corresponding data requirements. Basic production models address the relationship between fish production and water discharge, and the relationship between flooded surface and fish production. More refined production models focus on the impact of the dynamics of the flow, such as duration, timing, consistency. In addition to hydrology, environment must also be taken into consideration for a proper management of the fish resource.