A new study has suggested dam flow patterns could be harnessed to boost fishery yields - by up to nearly four-fold compared to un-dammed ecosystems, the American Association for the Advancement of Science has announced.
The study is based on the Mekong River basin, home to one of the largest freshwater fisheries in the world. 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 can greatly alter these flood pulses, and in turn impact fisheries, says the study. Research suggests optimizing the pulses, however, could leave fisheries better off.
In the study 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.