A major new assessment by the Convention on the Conservation of Migratory Species of Wild Animals (CMS) shows that some of the longest, most important freshwater fish migrations are in serious decline.
The Global Assessment of Migratory Freshwater Fishes is the most comprehensive review to date, identifying hundreds of species that rely on connected rivers across borders. Populations are falling due to dams, altered flows, pollution, overfishing, and climate pressures, as launched at the CMS 15th Meeting of the Conference of the Parties (COP15) in Brazil.
The analysis identifies 325 migratory freshwater fish species as candidates for coordinated international conservation efforts, highlighting a largely overlooked biodiversity crisis unfolding across the world’s shared river basins.
Migratory fish maintain river health, support inland fisheries, and sustain hundreds of millions of people. Their loss threatens ecosystems, food security, and local economies worldwide.
Priority rivers include the Amazon and La Plata–Paraná in South America, the Danube in Europe, the Mekong in Asia, and the Nile in Africa.
It also outlines practical tools governments can deploy immediately, including:
- protection of migration corridors and environmental flows,
- basin-scale action plans and transboundary monitoring, and
- coordinated seasonal fisheries.
Many migratory fish rely on long, uninterrupted river corridors connecting spawning grounds, feeding areas and floodplain nurseries, often across multiple countries. When dams, altered flows or habitat degradation interrupt those pathways, populations can decline rapidly. Since 1970, migratory freshwater fish populations worldwide have declined by roughly 81%, and nearly all (97%) of the 58 CMS-listed migratory fish species (including fresh and salt-water species) are threatened with extinction.
Healthy rivers mean healthy fish and communities. Coordinated, cross-border action can reverse declines and restore these remarkable migrations.