Basin-scale planning is needed to minimize impacts in mega-diverse rivers

The Mekong River Basin, site of the biggest inland fishery in the world, is undergoing massive hydropower development. Planned dams will block critical fish migration routes between the river's downstream floodplains and upstream tributaries. Here we estimate fish biomass and biodiversity losses in numerous damming scenarios using a simple ecological model of fish migration. Our framework allows detailing trade-offs between dam locations, power production, and impacts on fish resources. We find that the completion of 78 dams on tributaries, which have not previously been subject to strategic analysis, would have catastrophic impacts on fish productivity and biodiversity. Our results argue for reassessment of several dams planned, and call for a new regional agreement on tributary development of the Mekong River Basin.sustainable development | hydropower planning | fish species richness

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.

This paper draws on approaches in ecology, biology and policy analysis to examine the tensions between dams and fisheries in the Lower Mekong Basin. We review the exceptional importance of Mekong fisheries in terms of total catch, economic value and their role in rural livelihoods. The ecological conditions necessary to sustain the fish production are also analysed. The paper then considers the implications of dam development in the Mekong Basin, drawing on recent research to review predicted changes in hydrology and the resulting impacts on fishery resources. We then consider why, given the importance of fisheries, these potential impacts are not being addressed in regional policy processes.

No abstract

Gillnet sampling was conducted for a year in a tropical mangrove creek (SW Madagascar), characterized by a limited freshwater influence, a high turbidity and a tidal range up to 3 m. Sixty species of juvenile fishes were caught, 44 species being of commercial interest. Catches were dominated by Gerreidae (27% of total abundance), Teraponidae (16%), Carangidae (13%) and Sparidae (12%). The temporary resident fishes in the mangrove zone represented 50% of the species and 97% of the total abundance, the other species being rare (less than five individuals). The species richness, abundance and biomass per netting were low in the middle of the cool season (July-August). Monthly changes in the fish assemblage were particularly complex, with three species groups displaying a clear seasonal pattern, some species succeeding one another in a rather unstructured way, and three species abundant throughout the year. There was no clear structuring effect of temperature, salinity and turbidity on the fish assemblage. However, tidal, lunar and diel effects on the composition of the fish assemblage were evident. The species overlap between the Sarodrano mangrove fauna and the adjacent coral reef fauna is particularly weak with six species in common and shows that the mangrove plays only a very limited nursery role for coral reef species.

No abstract

No abstract