Some of the longest and most essential animal migrations on Earth take place beneath the surface of rivers. A major new report from the Convention on the Conservation of Migratory Species of Wild Animals (CMS), a United Nations environmental treaty, warns that many of these migrations are now rapidly breaking down.

The Global Assessment of Migratory Freshwater Fishes, released at the CMS 15th Meeting of the Conference of the Parties (COP15) in Brazil, finds that migratory freshwater fish are among the most threatened species worldwide. These fish are critical for maintaining healthy rivers, supporting major inland fisheries, and providing food and livelihoods for hundreds of millions of people.

Hundreds of Migratory Fish Species Need Global Protection

The assessment highlights hundreds of migratory fish species that require coordinated international action.…