Managing dams for sustainable fisheries

Tropical fisheries are some of the most productive and diverse in the world, and many who live near these fisheries depend on their catch as a primary source of protein. The Lower Mekong Basin is no exception to this, and houses fisheries which provide the people of the region with as much as 75% of their protein. Unfortunately, many of these tropical fisheries are under threat from human influences, including the construction of large hydroelectric dams. Is there some way that dams can be managed so that fisheries prosper?

A recent paper published by Sabo and colleagues explored this question. The underlying hypothesis centers around the flood pulse concept, which postulates that ecological systems in floodplains evolved under regular flooding conditions. Therefore, regular flooding should drive diversity and productivity within these systems. Sabo et al. used data driven models to explore how variation in the flood pulse should affect fisheries.

Based on historical fish catch and river flow data, the models show that fish catch in the Lower Mekong basin can be maximized with a long dry period punctuated by a strong flood pulse. This flood pulse should be characterized by multiple storm peaks. Traditionally, dams dampen variation in flooding regimes, muting flood pulses and shortening dry periods. However, if dams were managed with fisheries in mind, using practices which increase times between floods and flood pulse, fishery yields can be even greater than those predicted under restoration of natural flooding regimes (76% increase in managed versus 47% increase in restored). Unfortunately, under regimes which minimize dry periods and flood pulses, fish catch was predicted to see a 53% annual decline in yield.

Does this mean that dam operators should immediately switch to maximizing flood pulse and periods between flooding? Perhaps not. Despite these stunning results, it is important that dam operators partner with scientists to conduct long-term monitoring of fisheries and their response to dam operations. If we are to ensure food security of rural populations, responsible infrastructure development will be essential. Better understanding of how these large infrastructure projects affect fisheries and other food sources will allow us to plan for a more sustainable future.