Dams, fish and fisheries in the Mekong River Basin: Impacts of dams on fisheries
dams, reservoirs, migration, upstream, juvenile, Hydropower, turbines, mortality, spawning, barriers
Journal or Book Title
Catch and Culture
Dams and reservoirs block natural fish migration. Many of the commercial species in the Mekong have highly-developed migratory patterns. They generally move upstream to spawn and then juvenile fish move back downstream to feed and grow on the floodplains and wetlands (Poulsen et al., 2002). Dams act as a barrier to fish migrating upstream; and returning fish migrating downstream past hydropower dams generally must go through turbines. This results in mortalities. As a result, spawning is greatly reduced and replenishment of fish stocks is diminished. Some species which currently undergo long-distance migrations may be able to adapt to new environments if their present migration patterns are facultative or opportunistic, rather than obligatory. However, whether this will occur or not can only be determined after migration routes are blocked (see box below, detailing an expert group meeting on dams as barriers to fish migration in the Mekong, and possibilities for mitigation).