Mitigation of the impacts of dams on fisheries: A primer

The Lower Mekong Basin (LMB) in Cambodia, Lao PDR, Thailand and Viet Nam supports one of the world’s largest and most diverse capture fisheries, which provides food and livelihoods for many of the basin’s more than 60 million inhabitants. The Mekong’s fisheries are based largely upon catches from rivers and floodplains, which continue to provide excellent aquatic habitats and an annual flood pulse, the basis for much of the fisheries production. To support the needs of a growing population, many dams were built in the 20th century, especially for irrigation, and more are under construction or planned, including several very large dams for hydropower. Dams are designed to modify the environment and in the process may cause various negative impacts which can lead to loss of fisheries productivity and biodiversity, which is of particular concern in the Mekong Basin. This report explains in general terms some of the impacts of dams on fisheries and outlines some approaches to mitigation. The report aims to inform discussion on mitigation of impacts of new dams as well as to encourage mitigation of impacts caused by existing dams.