Freshwater fish populations plunge 81% as river migrations collapse

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. It provides strong evidence that fish relying on connected rivers across national borders are declining quickly due to dam construction, habitat fragmentation, pollution, overfishing, and climate-related ecosystem changes.

In total, 325 migratory freshwater fish species have been identified as candidates for international conservation efforts, pointing to a largely overlooked biodiversity crisis across shared river systems.

A regional breakdown of the 325 migratory freshwater fish species deemed candidates for international protection (beyond the 24 already listed) under the Convention's Appendices I (species requiring strict protection) and II (species needing international cooperation):

• Asia: 205
• South America: 55
• Africa: 42
• Europe: 50
• North America: 32

(The total adds to more than 325 because some species occur on multiple continents.)

Key river systems identified as priorities include South America's Amazon and La Plata-Paraná, Europe's Danube, Asia's Mekong, Africa's Nile, and the Indian sub-continent's Ganges-Brahmaputra.

Based on extensive global datasets and IUCN assessments of nearly 15,000 freshwater fish species, the report provides the most comprehensive overview so far of the conservation challenges facing migratory freshwater fish.

It also outlines practical steps governments can take immediately, including:

• protection of migration corridors and environmental flows,
• basin-scale action plans and transboundary monitoring, and
• coordinated seasonal fisheries

A Largely Overlooked Freshwater Biodiversity Crisis

Animals living in freshwater ecosystems are declining faster than those on land or in the oceans, yet the collapse of migratory freshwater fish has received relatively little global attention.

These fish depend on long, uninterrupted river pathways that link spawning grounds, feeding areas, and floodplain nurseries, often across multiple countries. When dams, altered water flows, or habitat degradation disrupt these connections, populations can drop quickly.

The report estimates that migratory freshwater fish populations have declined by about 81% worldwide since 1970. Nearly all (97%) of the 58 CMS-listed migratory fish species (including fresh and salt-water species) are now threatened with extinction.

The findings show that hundreds of migratory freshwater fish species are in poor conservation condition and emphasize that protecting them requires managing rivers as connected systems rather than treating them as separate national waterways.

Amazon Basin Highlights Urgent Conservation Needs

As host of COP15, Brazil has proposed several conservation measures focused on South America's largest river systems, the Amazon and La Plata-Paraná.

The Amazon Basin remains one of the last major strongholds for migratory freshwater fish, but increasing development pressures are putting that status at risk.

A case study released alongside the global assessment identifies 20 migratory fish species in the Amazon that meet the criteria for potential CMS Appendix II listing. These long-distance migratory species are central to regional fisheries, making up about 93% of total landings and supporting an industry worth an estimated US$436 million each year.

Some of these fish undertake remarkable journeys. The dorado (gilded) catfish (Brachyplatystoma rousseauxii), a bottom-dwelling species with metallic gold/silver coloring and a large body (up to 2 meters / 6.5 ft), completes the longest known freshwater migration of any fish. Its life cycle includes a journey of 11,000 kilometers from Andean headwaters to coastal nursery areas.

To strengthen conservation efforts, Brazil and other countries are proposing a Multi-species Action Plan for Amazonian Migratory Catfish (2026-2036), developed through regional cooperation.

Brazil has also proposed adding the spotted sorubim catfish (Pseudoplatystoma corruscans) to CMS Appendix II, emphasizing the need for coordinated action in the La Plata Basin, where these fish face threats from dams, altered water flows, and fishing pressure.

Together, these initiatives represent some of the most ambitious international efforts to protect migratory freshwater fish. They reinforce the central principle of CMS that conservation solutions must cover the full geographic range of migratory species and depend on cooperation between countries.

Experts Call for Coordinated Global Action

Lead Author Dr. Zeb Hogan:

"Many of the world's great wildlife migrations take place underwater. This assessment shows that migratory freshwater fish are in serious trouble, and that protecting them will require countries to work together to keep rivers connected, productive, and full of life."

CMS Executive Secretary Amy Fraenkel:

"This new assessment highlights a major priority for the conservation of migratory species and their habitats, that has not had adequate focus to date. By aligning science, policy and international cooperation, governments can safeguard the world's remaining great freshwater fish migrations and the communities and ecosystems that depend on them."

World Wildlife Fund-US, Vice President and Deputy Lead of Freshwater, Michele Thieme:

"Rivers don't recognize borders -- and neither do the fish that depend on them. The crisis unfolding beneath our waterways is far more severe than most people realize, and we are running out of time. Rivers need to be managed as connected systems, with coordination across borders, and investments in basin-wide solutions now before these migrations are lost forever."

By the Numbers: Global Migratory Fish Decline

• 325: Migratory freshwater fish species identified as candidates for coordinated international conservation action under the CMS (beyond the 24 species already listed in Appendices I and II).
• 205: Species identified in Asia alone, making it the global hotspot for migratory freshwater fish at risk.
• 81%: Estimated decline in migratory freshwater fish populations worldwide since 1970, one of the steepest drops recorded for any major vertebrate group.
• 97%: Share of CMS-listed migratory fish already threatened with extinction.
• 15,000: Freshwater fish species assessed through the IUCN Red List and global datasets used to produce this assessment, the most comprehensive evidence base ever assembled for migratory freshwater fish.
• 250+: Transboundary rivers and lakes worldwide, meaning conservation success depends on cooperation between countries rather than national action alone.
• 47%: Approximate share of Earth's land surface lying within shared river basins.
• 93%: Proportion of Amazon fisheries landings made up of migratory freshwater species, highlighting their critical role in regional food systems and livelihoods.
• US$436 million: Estimated annual value of Amazon fisheries based on migratory species
• 20: Amazon Basin species identified as meeting criteria for potential CMS Appendix II listing in the new case study.
• 10,000+ kilometers: Migration distance of the dorado (gilded) catfish among the longest freshwater migrations ever recorded.
• 1 fundamental solution: Managing rivers as connected ecological systems rather than isolated national waterways.

Documents in English, Spanish and French:

• Global Assessment of Migratory Freshwater Fishes (including the Amazon Basin case study: Potential CMS Appendix II candidate species)
• Multi-species Action Plan for Amazonian Migratory Catfish (2026-2036)
• Listing proposal: Spotted Sorubim (Pseudoplatystoma corruscans)