An unexpected way to boost fishery yields using dams

A new study based on the Mekong River basin, home to one of the largest freshwater fisheries in the world, reveals particular dam flow patterns that could be harnessed to boost food production – by up to nearly four-fold compared to un-dammed ecosystems. Because operation of dams can pose a threat to fisheries, and thus to food security, insights into smarter dam operations are critical. For many large tropical rivers, rainfall during the wet season drives a flood pulse that supports fish production, delivering protein and vitamins to millions of people. Hydropower dams, which are a critical source of electricity for many people worldwide, can greatly alter these flood pulses, and in turn impact fisheries. Some research suggests optimizing the pulses, however, could leave fisheries better off. Here, John Sabo and colleagues explored how controlled pulses from dams may alter fish abundance. They analyzed data collected between 1993 and 2012, which included the amount of fish biomass caught before the construction of a dam, from a well-studied tributary of the Mekong, the Tonle Sap River. Intervals between floods had the greatest impact on fisheries, the authors report, followed closely by the magnitude of pulse floods. They describe the ideal scenario where, artificially, seasonal floodplain drying would be prolonged, followed by a sudden transition to seasonal flooding. By modeling a hydrologic dam that adopted optimal flooding pulses over eight years, Sabo et al. identified a design that could offer fish yields that exceed a natural, pre-dam scenario by a factor of 3.7. LeRoy Poff and Julian D. Olden discuss these findings, as well as the broader implications for other rivers experiencing similar threats to sustainable fisheries, in a related Perspective.


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