- Around the world, migratory freshwater fish are in peril from activities including overfishing and, more recently, dams blocking their migratory routes.
- The most threatened species include two large Amazonian catfish, and an inaugural conservation plan will be implemented by the five countries where they range.
- Connected river habitat is crucial for the gilded catfish and Laulao catfish: They undertake some of the longest known river migrations in the world, traveling up to 12,000 kilometers (7,500 miles) over their lifetimes.
- The main challenge in saving these migratory catfish and many other aquatic species is maintaining connectivity among rivers, which in the Amazon are increasingly being affected by dams and shipping.
The background was right for the announcement of the bad news. Fish swam in a wall-sized tank that framed a table of scientists and environmentalists in the auditorium of the Pantanal Biopark, the world’s largest freshwater public aquarium, in the Brazilian city of Campo Grande. They’d gathered for the launch of a report on the state of the world’s freshwater migratory fish.
The event opened with a dire statement from a top official from Brazil’s environment ministry: “The numbers are chilling,” said Rita Mesquita, the ministry’s secretary of biodiversity.
Mesquita was there to address the 15th Conference of the Parties to the U.N. Convention on Migratory Species (CMS COP15), a treaty adopted in 1979 that focuses on conservation of migratory animals and their habitats. Currently, 132 nations and the European Union are signatories. The meeting, which took place in Campo Grande, the capital of the Brazilian state of Mato Grosso do Sul, from March 23-29, also drew experts and civil society representatives from across the globe.
This was the first time in more than a decade that experts analyzed data on global ichthyofauna: fish life. The last assessment, conducted in 2011, examined the status of 3,000 species. The new round was far more comprehensive, covering 15,000 species. Of these, 349 are migratory, almost all of them threatened.
The CMS report recommended that 325 of those species be added to the convention’s appendices. Migratory species threatened with extinction are listed on Appendix I, giving strong protections, while species that need international cooperation are listed on Appendix II. All signatory countries must commit to adopting conservation measures. Currently, the CMS appendices list 1,200 migratory species.
During their life cycles, freshwater fish cross borders and biomes, which complicates conservation efforts. Prior to this COP15 meeting, only 58 fish species (both freshwater and ocean fish) were listed in the convention’s appendices
They include the European eel (Anguilla anguilla); 19 species of sturgeon from the genus Acipenser, and two threatened Amazonian fish: the gilded catfish (Brachyplatystoma rousseauxii, called dourada in Brazil) and the Laulao catfish (Brachyplatystoma vaillantii, known in Brazil as piramutaba). Populations of the latter two have declined by 90% since the 1970s.
Migratory freshwater fish are a dietary staple for people around the world. In Brazil, for example, the pintado (Pseudoplatystoma corruscans), also known as the spotted sorubim, is found in supermarkets and street markets across the country. This catfish, which migrates through the Plata River Basin, is listed as near threatened, and at COP15 it was added to Appendix II of the convention.
The greatest challenge these migratory fish species face is the loss of connectivity between river basins. They require intact corridors and an integrated conservation strategy. Conservation is especially difficult where river connections are undergoing major changes because of dams, diversion for irrigation or other disruptions.
“The region that stands out for immediate action, and is able to take immediate action, is South America,” National Geographic explorer Zeb Hogan told delegates at the CMS conference. He is lead author of the report and an ecologist at the University of Nevada in the U.S., told delegates at the CMS conference.
He highlighted the region because many of its basins have preserved river connectivity, including parts of the Amazon biome, home to fish that migrate vast distances.
The Amazon at the center of the debate
In discussions about the critical state of freshwater migratory species, the two large Amazonian catfish received extensive attention at COP15. The dourado is listed as vulnerable on the IUCN Red List. In speeches at the meeting, CMS executive secretary Amy Fraenkel cited the species to emphasize the importance of transnational actions to conserve migratory species.
Few species represent ecosystem connectivity as well as the dourado (known as dorado in Peru and Bolivia, and zúngaro dorado in Colombia and Ecuador). In 2017, leading Amazonian fish experts Ronaldo Barthem, Michael Goulding and others discovered that this catfish undertakes the world’s longest freshwater migration, a feat previously attributed to salmon. Their findings were published in the journal Scientific Reports.
During its 12- to 15-year lifespan, the dourado migrates some 8,000-12,000 kilometers (about 5,000-7,500 miles), or a total distance nearly the length of South America. It’s spawned in the Andean foothills, and the larvae are carried downstream, as far as the mouth of the Amazon River. By that time, the larvae have developed into juvenile fish, and they feed and grow in the nutrient-rich waters of the estuary over the next few years. The adult fish then make the journey back upstream to their spawning grounds, where the cycle repeats.
This catfish has major economic importance for Amazonian communities, supporting thousands of artisanal fishers and feeding millions of people. As an apex predator, it also plays an outsized role in keeping the Amazon river system in balance.
An important step taken during the CMS conference was the unanimous approval of a conservation action plan, proposed by Brazil, for migratory Amazonian catfish. The bid was always expected to pass, given that the dourado and piramutaba were listed at the previous CMS conference, in Uzbekistan in 2024. The piramutaba is severely impacted by industrial fishing in the mouth of the Amazon River.
With sharp population declines over recent decades, action is considered critical. Some researchers point to a probable collapse of both species in parts of the Amazon, including in the basin of its largest tributary, the Madeira River.
“Now is the time to get down to business,” said Carolina Doria, an official with Brazil’s fisheries ministry. She noted that joint efforts are needed by the five Amazonian countries where these large migratory catfish range: Brazil, Bolivia, Colombia, Ecuador and Peru.
That includes “harmonizing” these countries’ fisheries statistics, she said. In Brazil, there’s a severe lack of data; only recently has the country resumed systematizing data on landings of the most-captured species in the Amazon.
Hydropower dams: A stumbling block
After decades of pressure by industrial fishing, research shows that dams now pose the main threat to the dourado and piramutaba by blocking their migrations. Before serving as an official at the fisheries ministry, Doria was a professor at the Federal University of Rondônia. One of her studies revealed that dourado landings in fishing ports fell by 50% after the Madeira River Hydroelectric Complex in the southwestern Amazon came online in 2010.
Evidence of the ecological impacts of Brazil’s two Madeira River dams is also reported by fishers, especially those farther upstream in Bolivia, at the headwaters of the rivers.
Omar Orellana, president of the Fishers’ Association of Puerto Villa Royale in Bolivia, attended COP15, where he talked to journalists and spoke on panels organized by the Amazonian Waters Alliance, a coalition of more than 30 nations focusing on the health and connectivity of the Amazon Basin
In his speeches, he reported drastic changes in the quantity and size of fish in the upper reaches of the Madeira basin. “In the 2000s, we started seeing a decline. Then, they appeared during the offseason until they disappeared completely in 2014,” he said.
His experience is backed by research documenting this same trend. A study led by French researcher Fabrice Duponchelle, and co-authored by Doria, reported a 93% loss of dorados in the Upper Mamoré, one of the main tributaries of the Madeira.
Before the two dams were built, B. rousseauxii accounted for 5.5% of local fishers’ catches; after the construction, it dropped to 0.4%. “What we are seeing is the collapse of the dorado in that part of the Madeira,” said report co-author Paul Van Damme, who heads Faunagua, a Bolivian nonprofit that studies migratory species.
He said the main problem with the Madeira dams is that the so-called fish ladders, a system of channels to allow fish migrating upstream to detour around the dams, don’t work. Adult fish can’t get upriver, and so, without migration, the population in the upper parts of the basins isn’t being renewed.
This was raised as a serious issue during the dams’ environmental licensing process: that they would create a transboundary problem on a key route for migratory catfish. Though Brazil led the action plan proposal at COP15, the government will not take responsibility for the impacts caused in Bolivia, Van Damme said, and there’s no discussion about possible compensation.
The Santo Antônio and Jirau dams on the Madeira are only part of growing connectivity threats. Despite concerns over environmental damage and Indigenous rights issues, expansion of the Madeira River waterway is underway. It includes intensive dredging to facilitate freight shipments for export, particularly soy; last year, 77% of Brazil’s soy exports went to China. The project is part of Brazil’s infrastructure investment plan known as the New PAC.
Now, studies are underway to license a new transnational power plant in the Madeira River Basin. The Guajará-Mirim dam, which would be built on the Mamoré River, is projected to be even larger than the two existing hydropower plants and includes the construction of locks for ships to travel between Brazil and Bolivia. Locks pose significant barriers for migrating fish.
Next steps in the action plan
Building on existing coordination between stakeholders could help stem drastic catfish declines. The new action plan was created with input from NGOs, fishers and governments of Amazonian countries. The Amazon Waters Alliance, launched a decade ago, is one key voice. Last year, it organized what it called a “dialogue of knowledge,” where fishers from several countries discussed ways to collaborate on protecting fish stocks.
Another alliance initiative uses citizen science is to consolidate databases among Amazon Basin countries. The Ictio app enables fishers, riverine communities and market vendors to post information on the species and quantities available. Between 2018 and 2025, approximately 600,000 observations were uploaded. During COP15, it was suggested that this data could help support implementation of the action plan.
Still, hydroelectric dams are likely to remain the toughest challenge to successful action among the five Amazonian countries through which large migratory catfish pass.
Brazil and Bolivia are moving forward with their plan to build the binational power plant on the Mamoré River, and Peru has started reviewing plans for dams in the foothills of the Andes. These are seen as the works with the greatest potential impact on the Amazon’s migratory fish species.
The Peruvian Amazon Research Institute (IIAP), a government outfit, is participating in the country’s energy planning to prevent new projects from affecting connectivity between rivers that link the Andes to the Amazon.
Mauro Ruffino, who coordinates the Amazon Cooperation Treaty Organization, noted that catfish conservation across the region began 30 years ago, with meetings between Brazil and Colombia to enforce joint fishing restrictions. (The treaty organization oversees an international agreement aimed at joint protection and development of the Amazon.)
While progress didn’t materialize immediately from those initial talks, Ruffino said he believes that now, with the broad coordination that helped gain approval for the migratory catfish protection proposal at the CMS conference, the results will be positive.
“Without collaboration, there is no connectivity in the Amazon,” Ruffino said.
Banner image: Amazonian migratory catfish for sale at the Ver-o-Peso market in Belém. Image by AP Photo/Eraldo Peres.
This story was first published here in Portuguese on April 7, 2026.
325 Long-neglected migratory freshwater fish species need protection now: Report
Citations:
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Hauser, M., Doria, C. R., Pécheyran, C., Ponzevera, E., Panfili, J., Torrente‐Vilara, G., … Duponchelle, F. (2024). Quantitative impacts of hydroelectric dams on the trans‐Amazonian migrations of goliath catfish. Conservation Letters, 17(5). doi:10.1111/conl.13046
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