- The gilded and piramutaba catfish (Brachyplatystoma rousseauxii and B. vaillantii, respectively) were recently placed on the Convention on the Conservation of Migratory Species (CMS) list, also known as the Bonn Convention.
- These fish carry out the longest freshwater migration on the planet: The gilded or “dorado” travels 11,000 kilometers (6,800 miles) between the mouth of the Amazon River and the foot of the Andes to lay its eggs; the piramutaba swims 5,500 km (3,400 mi).
- Both species are endangered due to overfishing and construction of hydroelectric plants on rivers in the Amazon; the dorado’s distribution range has shrunk by 37% because of the dams.
Of the approximately 2,500 fish species found in the Amazon Basin, two catfish are special both to state economies in the region and to global biology: the gilded or dorado (Brachyplatystoma rousseauxii) and the piramutaba (B. vaillantii).
Not only widely appreciated in the culinary world and selling at high prices, these fish are the farthest-migrating freshwater species: the dorado swims approximately 11,000 kilometers (6,800 miles) during its life cycle.
But last year, the dorado’s status was updated to vulnerable on the IUCN Red List. The piramutaba is not yet listed, but is expected by specialists to be placed on the list soon.
Another step was taken in Samarkand, Uzbekistan, in February to call global attention to the survival of these emblematic Amazon species. At the Convention on the Conservation of Migratory Species (CMS), also known as the Bonn Convention, treaty holders voted to place the dorado and piramutaba on their list.
“In recent years, the dorado’s occupation and migration area has shrunk by 37% because of dams built in the Madeira River Basin,” affirms biologist Guillermo Estupiñán, fisheries resource specialist for the Wildlife Conservation Society. Estupiñán attended the event, during which the Brazilian government presented a proposal that the species be included in the convention’s Appendix II.
Estupiñán explains that the migratory animals listed in Appendix I are those in most urgent need of protective measures because they are very threatened. Those in Appendix II are species just beginning to concern specialists, who recommend that measures be taken to improve their conservation status and therefore keep their threat of extinction at bay.
“The dorado and piramutaba are the first Amazonian fish to be placed on the CMS list,” he states. “Being placed in Appendix II is very important for preserving the species and their habitat, whose migratory routes pass through more than one country. This means dialogue and cooperation must be promoted between the governments of the places they inhabit, in this case Brazil, Peru, Bolivia, Colombia, Ecuador and Venezuela.”
The world’s longest freshwater migration
These two large catfish found in northern Brazil do not have scales. This is one reason they are favored by local chefs — being scaleless means they are much easier to clean and debone than other fish. The dorado is the larger of the two, growing up to 80 centimeters (31 inches) in length and weighing as much as 40 kilograms (88 pounds) while the piramutaba grows up to 40 cm (16 in) in length as an adult, weighing 6-8 kg (13-18 lbs).
What makes the life cycles of both fish so peculiar and so vulnerable in today’s world are the long distances they travel during migration.
It is estimated that the piramutaba travels some 5,500 km (3,400 mi) from the Amazon River estuary in Belém — a food-rich region where the river transitions into the sea — to Iquitos, Peru, where it lays its eggs. The fry are then carried by the current back to the main river channels, including the Solimões and the Amazon.
But the dorado’s journey is the most impressive of the two because it swims all the way back to the place where it hatched in the foothills of the Andes to reproduce — a migratory route stretching 11,000 km, the longest of any freshwater species known to the scientific world.
The distance is as if the species were to swim on an imaginary river stretching from Boa Vista, Roraima, to Porto Alegre, Rio Grande do Sul, and back — cities located in the far north and far south of the country, respectively.
But in recent years, the courses of the rivers followed by the dorado and piramutaba have been altered. Two large hydroelectric dams — the Jirau and Santo Antonio — were built on the Madeira River between 2008 and 2016. They are among the world’s largest dams.
The impacts on the two species have been enormous, researchers like Estupiñán say. The same is occurring in neighboring countries.
“The danger is everywhere. Dams are being built in Brazil and other Amazonian countries as well. Theirs aren’t as large as ours, but they were built on tributaries that form the basin,” states Carolina Doria, biology professor at Rondônia Federal University.
According to her, the number of gilded catfish captured in Bolivian tributaries upstream from the Brazilian hydroelectric plants fell by more than 70% . “This shows that a large volume of fish can no longer migrate because of these dams. Connectivity has been lost.”
Lack of fisheries statistics
The dams are not the only factor causing population decline of these Amazonian catfish, which are predators at the top of the food chain — they are also suffering because of fishing.
More information exists on the dorado, but specialists know the piramutaba is affected by the same threats. There are, however, no official statistics, only studies funded by organizations or that make up academic research.
“Not a single report on fishing landings has been released by a public agency or institution responsible for fisheries in Brazil since 2011. And the last time data were collected at the busiest ports in Amazonia was in 2004,” affirms Estupiñán.
In practice, this means no one has any idea which fish were caught, where they were caught and how many were caught inside the Amazon Basin over these years. Neither is it known how many are sold at the region’s busiest ports. How is it possible to protect threatened species without knowing how many or what kind of fish are being caught?
Still, the current administration seems to be more interested in the problem. Fisheries and aquaculture now have their own ministry — under the previous administration, they were a mere secretariat. The current agency will support fisheries monitoring throughout the Brazilian Amazon Basin for a renewable one-year period starting in 2024.
“We want to find out what sort of pressure these species and their populations are facing. We will analyze data like biometrics and fish landings,” says Doria, who will be part of the study.
It is important to note that the dorado and piramutaba are not the only species at risk. One unprecedented study recently warned that 44% of all migratory species are showing reduced populations worldwide. The report State of the World’s Migratory Species states that the situation is even more worrisome for fish, with a 90% drop in population of 37 migratory fish species since the 1970s. “The impact that the species on the Madeira River have suffered will be difficult to revert. Right now, the goal is to keep it from increasing as new dams are constructed in the region. And joint action between a number of nations will be crucial for this to work,” Doria concludes.
Banner image: Piramutaba (Brachyplatystoma vaillantii). Image by Clara Costa D’Elia via Wikimedia Commons (CC BY 4.0).
Citations:
Leite Lima, M. A., Rosa Carvalho, A., Alexandre Nunes, M., Angelini, R., & Rodrigues da Costa Doria, C. (2020). Declining fisheries and increasing prices: The economic cost of tropical rivers impoundment. Fisheries Research, 221, 105399. doi:10.1016/j.fishres.2019.105399
State of the World’s Migratory Species. (2024). Retrieved from Convention on the Conservation of Migratory Species of Wild Animals website: https://www.cms.int/en/publication/state-worlds-migratory-species
This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Mar. 6, 2024.