Reconnecting rivers: a critical path to saving migratory fish
© Zig Koch / WWF
Connected rivers are the backbone of ecosystem-scale resilience. They move water, nutrients, and animals through landscapes and across borders. Yet for migratory freshwater fishes, the rivers they depend on are increasingly fragmented and disconnected by human infrastructure and over-extraction. The Convention on the Conservation of Migratory Species of Wild Animals (CMS) offers a powerful, underused tool to help rivers and other inland waters receive holistic protection and restoration, instead of the current system of piecemeal conservation.
CMS is a UN treaty that provides a platform for countries to coordinate international action for animals that cross human-drawn borders. Appendix I of the CMS mandates strict protection for endangered migratory species, and Appendix II enables cooperative agreements among countries for threatened species. In practice, the CMS mobilizes agreements and species action plans across multiple countries.
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81% decline of monitored populations of migratory freshwater fishes since 1970
The power of the CMS matters immensely for freshwater habitats and wildlife. Monitored populations of migratory freshwater fishes have declined 81% since 1970 according to the 2024 WWF Living Planet Report. The drastic decline is driven largely by habitat loss, overfishing, and river fragmentation that blocks migration routes. Reversing these trends requires reconnecting rivers and safeguarding critical spawning and feeding habitats through dam and levee removals, fish passage, fisheries reserves, sustainable management and floodplain restoration. The tricky part is that rivers often cross borders and migratory paths from feeding grounds to spawning sites extend hundreds, sometimes thousands of miles. So inland water conservation is more complex than simply designating a specific area as off limits to human activity.
In March, the Parties to the CMS will meet in Campo Grande, Brazil, home to the Pantanal, the largest tropical wetland in the world. Ahead of that Conference of the Parties, researchers including WWF’s Michele Thieme (Vice President and Deputy Lead of Freshwater for WWF-US) are calling on CMS Parties and partners to add more threatened transboundary migratory freshwater fishes to the CMS Appendices and to use CMS instruments (like treaties and MOUs) in countries and rivers where CMS membership is limited, like the Mekong and Amur. They also urge improved life‑history research, updated IUCN assessments, and stronger science‑policy communication to turn research into action that can reverse the downward curve for freshwater species.
© Freshwaters Illustrated
These steps would unlock the CMS’s potential to coordinate protection across borders and advance basin‑scale management where it’s most needed. Increased recognition for freshwater species and whole river basin health in the CMS would encourage countries to prioritize protecting, conserving, and restoring inland waters, and assist country efforts to identify the wetlands and rivers that are most critical to target for restoration and protection. Aligning country conservation priorities with CMS listings can structure cross‑border cooperation, fast‑track joint action plans, and attract financing to make conservation happen - boosting resilience for freshwater fishes and all life that relies on connected rivers to thrive.