Epic migrations of freshwater fish, among the world's great natural wonders, are rapidly collapsing, according to the most comprehensive assessment to date from the UN's Convention on the Conservation of Migratory Species (CMS). The report, led by Dr. Zeb Hogan of the University of Nevada, found that freshwater fish populations worldwide have crashed by about 81% since 1970.
The longest migration of any freshwater fish is that of the dorado catfish, which travels up to 7,000 miles from the foothills of the Andes to the Amazon estuary and back. Such migrations are under threat from pollution, dams, overfishing and the climate crisis, which raises water temperatures. Migratory fish sustain hundreds of millions of people but are among the most imperilled wildlife on the planet.
The CMS is meeting this week in Brazil, where the Amazon remains one of the last strongholds for migratory species. Measures to protect them include removing barriers, ensuring water flows, tackling pollution and coordinating fisheries. The report identified 325 migratory freshwater fish species that cross borders and could be listed for protection, but only 24 are currently listed.
Key river basins in trouble include the Mekong, where all large migratory fish are at risk of extinction. However, none of the major Mekong nations are yet CMS members. Other priority basins are the Danube, Nile and Ganges-Brahmaputra. The report calls for urgent international cooperation to prevent these migrations from being lost forever.
