Water requirements of floodplain rivers and fisheries: existing decision support tools and pathways for development

Fisheries are some of the most valuable natural resources that depend upon natural regimes of river flow for their productivity and full development benefits. Managing rivers to sustain these benefits requires that environmental flow requirements of river fisheries be understood and conveyed effectively into decision-making processes at multiple levels within the river basin. The present research report reviews existing environmental flow methodologies and fisheries production models to determine which combination of existing approaches will provide most potential for development of such decision support tools. This is the first comprehensive review of the use of environmental flow methodologies for managing large rivers and floodplains for fisheries production. Previous reviews have focused exclusively on the fisheries models themselves and have not explored how these models can be combined with other approaches to understand and predict the impact of changes in river flow regimes on fisheries production. In view of the importance of river fisheries in the livelihoods of the rural poor across much of the tropics, more effective decision-support tools that improve the ecological basis of water management in river basins can play an important part in increasing fisheries productivity and the health and livelihoods of rural populations at the basin scale. The review concludes that the methodology DRIFT (Downstream Response to Imposed Flow Transformation) combined with use of Bayesian networks and age-structured fisheries models will provide the most promising direction for future research. There will however be cases where this approach will not work and flexibility in the use of other environmental flow methodologies and tools will be required. The target audience for this review includes river and fisheries scientists concerned with improving water management for the poor of the developing world, and river scientists and managers in general. The results of the research can be best applied through the development of improved environmental flow and fisheries modeling approaches, including studies in the focal basins of the CGIAR Challenge Program on Water and Food.