The world’s rivers are witnessing a silent crisis. A new United Nations report reveals a staggering 81% decline in migratory freshwater fish populations since 1970, a collapse that threatens not only biodiversity but also the livelihoods of hundreds of millions of people who depend on these species for food and income. From the epic journeys of the dorado catfish in the Amazon to the familiar routes of salmon and eels, these remarkable migrations – some of the largest animal movements on Earth – are rapidly disappearing.
The assessment, led by Dr. Zeb Hogan of the University of Nevada and conducted by the UN’s Convention on the Conservation of Migratory Species (CMS), paints a grim picture of a largely overlooked environmental disaster. Dr. Hogan explained the scale of what’s at stake: “It’s incredibly hard to imagine what’s going on beneath the water when you look at a river – but you have billions of fish making these epic migrations.” The dorado catfish, for example, undertakes a 7,000-mile (11,000km) round trip annually, spawning in the Andes foothills and feeding in the Amazon estuary, reaching lengths of up to 2 meters.
But these incredible journeys are increasingly imperiled. The report identifies 325 migratory freshwater fish species that cross international borders and could qualify for protective action under the CMS treaty, yet only 24 are currently listed, primarily sturgeon species valued for their caviar. This lack of coordinated conservation efforts, coupled with a host of human-induced pressures, is driving these populations toward extinction.
The Multiple Threats Facing Freshwater Fish
The decline of migratory freshwater fish is a complex issue driven by a confluence of factors. Pollution from agricultural runoff and industrial discharge contaminates rivers and lakes, harming fish and disrupting their reproductive cycles. Dams, while providing hydroelectric power and irrigation, act as significant barriers to migration, fragmenting populations and preventing fish from reaching crucial spawning grounds. Overfishing, both legal and illegal, further depletes already stressed stocks. And increasingly, the climate crisis is exacerbating these problems, raising water temperatures and altering river flows.
“Freshwater species are especially vulnerable,” explains the CMS Executive Secretary, Amy Fraenkel. “Their journeys, which can cross multiple national borders and even continents, are extraordinary feats of timing and endurance. But these species face mounting pressures at every stage of their life cycles. International cooperation is essential to ensure that such species survive and thrive.”
A Critical Food Source at Risk
The loss of migratory freshwater fish isn’t just an ecological tragedy; it’s a humanitarian one. These fish underpin some of the world’s largest inland fisheries, providing a vital source of protein and income for hundreds of millions of people. The Tonlé Sap lake in Cambodia, part of the Mekong river system, is a prime example. Dr. Hogan notes that fishermen there “can catch several tons of fish in an hour,” highlighting the immense productivity of these ecosystems and the dependence of local communities on them.
International Cooperation is Key
Currently, 132 countries are party to the CMS treaty and are meeting this week in Brazil to discuss conservation strategies. The COP15 summit is focusing on improved international cooperation to protect migratory fish, with proposed measures including dam removal or mitigation, ensuring adequate water flows, tackling pollution, and coordinating fisheries management. The Amazon basin, one of the last strongholds for migratory freshwater fish, is a key focus of these discussions.
Though, the report emphasizes that the crisis is largely overlooked. While half of the Earth’s land surface lies within transboundary river basins, only a fraction of the 325 migratory fish species identified as needing protection have been formally listed under the CMS. Michele Thieme of WWF-US stresses the urgency: “Rivers don’t recognise borders – and neither do the fish that depend on them. The crisis unfolding beneath our waterways is far more severe than most people realise, 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.”
The Mekong River basin is particularly vulnerable, with all of its large migratory fish species now at risk of extinction, including the giant catfish, whose population has declined by half in recent years due to overfishing and habitat loss. Critically, none of the key Mekong nations – Thailand, Cambodia, Laos, and Vietnam – are currently members of the CMS treaty, hindering regional conservation efforts. Brazil is prioritizing gaining their membership at this summit.
Hopeful Signs and Future Action
Despite the bleak outlook, there are glimmers of hope. Brazil and other countries have proposed a decade-long action plan for migratory catfish, which could serve as a model for other river basins. Dr. Hogan believes that “the action that we’re seeing in the Amazon is very hopeful. Keeping rivers free flowing and healthy is incredibly important.” efforts to improve river connectivity through dam removal are gaining momentum in both Europe and the United States.
The report also highlights the tragic example of the Chinese paddlefish, which went extinct in the Yangtze River, largely due to the construction of the Gezhouba hydroelectric dam in 1981. This serves as a stark warning of the irreversible consequences of unchecked development.
The CMS COP15 in Brazil represents a critical opportunity to address this escalating crisis. The coming months will be crucial in determining whether international commitments translate into concrete actions to protect these vital migratory fish populations and the ecosystems and communities that depend on them. Updates on the outcomes of the COP15 summit and the implementation of new conservation measures will be available on the CMS website.
What do you think should be done to protect these vital ecosystems? Share your thoughts in the comments below, and please share this article to raise awareness about this critical issue.
