Migratory freshwater fish populations have crashed by 81 percent since 1970, a staggering decline that outpaces losses in both terrestrial and marine species. A new global assessment published in May 2026 found that 65 percent of these fish species are now threatened with extinction. The findings come from the Living Planet Index for Migratory Freshwater Fish, a collaboration between the World Fish Migration Foundation, the Zoological Society of London, and other research groups.
A river of trouble: dams, overfishing, and climate change
The study analyzed data on 1,864 populations of 284 migratory freshwater fish species across the world. The biggest driver of the decline is dam construction. Dams block migration routes that fish have used for millennia to reach spawning grounds. Overfishing is the second most common threat, followed by pollution and climate change. The researchers noted that the rate of decline has accelerated in recent decades, with no sign of slowing.
Where the losses hit hardest
South America and Europe saw the steepest drops. In South America, populations fell by 91 percent. Europe recorded a 75 percent decline. The Amazon, the Mekong, and the Danube river basins were among the hardest hit. The golden dorado, a prized sport fish in Argentina and Brazil, has disappeared from parts of the Paraná River after dam construction. The European eel, which migrates from freshwater rivers to the Sargasso Sea to spawn, has declined by 90 percent since 1980. Local communities that depend on these fish for food and income are feeling the effects directly. In Cambodia, the Mekong giant catfish once provided a major protein source for villages along the river. Now it is critically endangered.
A narrow window for action
The report's authors say the situation is urgent but not hopeless. They point to successful restoration projects in the United States and Europe where dam removals have allowed fish populations to rebound. In the Penobscot River in Maine, removing two dams helped restore Atlantic salmon and river herring runs. In Finland, restoring river connectivity boosted brown trout numbers. The researchers call for a global target to restore 250,000 kilometers of free flowing rivers by 2030. They also recommend stronger enforcement of fishing regulations and better management of water extraction. Without these measures, the report warns, many of the world's migratory freshwater fish species could vanish within decades.
