This 6-foot-long, 200-pound catfish is a goliath—and makes an epic migration
That number, though, doubled in February, when the dorado, along with another goliath catfish from the Amazon, the piramutaba, became the first two fish species from the Southern Hemisphere to be covered under the treaty.
The news was greeted enthusiastically by many fish experts, including Barthem, an ecologist with the Goeldi Museum in Belém, Brazil: “It’s perhaps the most promising initiative to promote the conservation of the aquatic ecosystems” in the Amazon, he says.
For instance, the listing could promote collaboration between governments across the species’ migration route, leading to better conservation plans, says Susan Lieberman, vice president for international policy at the Wildlife Conservation Society in the U.K.
A richness of migratory fish
As apex predators, the Amazon’s seven species of goliath catfish play a fundamental role in the balance of the river system. What’s more, migratory fish account for 80 percent of the Amazon’s commercial fish production; both artisanal and industrial fisheries closely track the seasonal movements of the dorado and piramutaba.
For the new study, researchers also relied on catch data, larval studies, and field observations to gain insight into these fishes’ movements. (Learn how a species is found daily in the Amazon.)
The life of the dorado begins close to the Andes, where the fish are born before they drift as larvae and juveniles downstream toward the mouth of the river. The fish, which can live up to 17 years, later return as sub-adults to the western Amazon to spawn, crossing several countries, including Brazil, Bolivia, Colombia, Ecuador, and Peru. The smaller piramutaba makes similar, if shorter, migrations, though its exact spawning grounds are unknown.
“Homing, a behavior that causes these fish to return to the place where they were born to spawn, indicates that this may be a memory that resists distance and the different environments along their migratory routes,” says Guillermo Estupiñán, a goliath catfish expert with the Wildlife Conservation Society in Brazil.
The massive annual flood pulse that transforms the Amazon and its more than a thousand tributaries, submerging forest-covered wetlands and creating a mosaic of different habitats, also favors the migratory behavior of fish in search of breeding or feeding grounds.
The recent study in Fish and Fisheries showed there are at least 223 species of migratory fish in the Amazon, but the true number is probably far higher. (Read about another enormous fish that undertakes a long migration.)
For the goliath catfish, overfishing remains a main concern: In 2007, scientists estimated an annual dorado harvest of at least 10,500 tons in the Amazon Basin. Brazil has not updated such statistics since, though there are plans to resume monitoring, says Lisiane Hahn, a fish biologist who runs a Brazilian company called Neotropical Environmental Consulting.
But hydroelectric dams may present a more existential threat. While no dams exist on the main stem of the Amazon, there are long-standing plans to build hundreds of them throughout the rest of the river system—structures that could cut off migration routes for goliath catfish. (Learn how megadams threaten the world’s biggest fish.)
