This 6-foot-long, 200-pound catfish is a goliath—and makes an epic migration

When Ronaldo Barthem began learning the dorado, a form of goliath catfish, in an estuary of Brazil’s Amazon River several decades ago, he was puzzled by the absence of adult fish. Where, he wondered, did the golden-hued animal, which can grow as a lot as six feet long, stride to spawn?

Years of investigation revealed a dazzling answer: The dorado swims via several countries, all the way to the foothills of the Andes on the opposite aspect of the continent, to finish its existence cycle. The 7,000-mile roundtrip saunter is by far the longest migration made by any freshwater fish on this planet, according to recently published research in the journal Fish and Fisheries.

The epic migration has seemingly helped the dorado increase its growth and survival, as younger animals on the transfer have the relieve of a colossal range of meals, from algae to bugs. But its prolonged saunter across national borders has also made the species, which may weigh extra than 200 pounds, extra vulnerable to human threats, from overfishing to hydropower dams. 

These are the same reasons migratory freshwater fish have declined by 76 percent since 1970, ranking them among probably the most endangered groups of animals on this planet. (Read why we detached haven’t caught the greatest freshwater fish.)

Despite their dire situation, migratory fish have historically been equipped cramped protection. Of the 1,200 animals listed in the Convention on Migratory Species, a UN-governed international treaty, legal two are migratory fish: the critically endangered Mekong giant catfish and the lake sturgeon.

That quantity, although, 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 lined under the treaty.

The news was greeted enthusiastically by many fish consultants, together with Barthem, an ecologist with the Goeldi Museum in Belém, Brazil: “It’s perhaps probably the most promising initiative to advertise the conservation of the aquatic ecosystems” in the Amazon, he says.

For instance, the listing may presumably promote collaboration between governments across the species’ migration route, leading to better conservation plans, says Susan Lieberman, vice chairman for international policy at the Wildlife Conservation Society in the U.Adequate.

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 machine. What’s extra, migratory fish account for 80 percent of the Amazon’s commercial fish production; both artisanal and industrial fisheries closely track the seasonal actions of the dorado and piramutaba.

For the original look, researchers also relied on catch data, larval experiences, and subject observations to gain insight into these fishes’ actions. (Learn how a species is discovered daily in the Amazon.)

The existence of the dorado begins shut to the Andes, where the fish are born ahead of they drift as larvae and juveniles downstream toward the mouth of the river. The fish, which can stay as a lot as 17 years, later return as sub-adults to the western Amazon to spawn, crossing several countries, together with Brazil, Bolivia, Colombia, Ecuador, and Peru. The smaller piramutaba makes similar, if shorter, migrations, although its exact spawning grounds are unknown.

“Homing, a behavior that causes these fish to return to the place where they have been born to spawn, indicates that this may be a memory that resists distance and the varied environments along their migratory routes,” says Guillermo Estupiñán, a goliath catfish knowledgeable with the Wildlife Conservation Society in Brazil. The massive annual flood pulse that transforms the Amazon and its extra than a thousand tributaries, submerging wooded area-lined wetlands and creating a mosaic of varied habitats, also favors the migratory behavior of fish in search of breeding or feeding grounds. 

The latest look in Fish and Fisheries confirmed there are at least 223 species of migratory fish in the Amazon, however the legal quantity is probably far greater. (Read about another gigantic fish that undertakes a long migration.)

For the goliath catfish, overfishing remains a main pains: In 2007, scientists estimated an annual dorado harvest of at least 10,500 a lot in the Amazon Basin. Brazil has no longer updated such statistics since, although 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 demonstrate a extra existential threat. Whereas no dams exist on the main stem of the Amazon, there are long-standing plans to fetch loads of of them all the way via the remainder of the river machine—constructions that may presumably in the reduction of off migration routes for goliath catfish. (Learn how megadams threaten the area’s greatest fish.)

Hahn spent eight years tagging and tracking loads of of dorados and piramutabas in the Madeira River after two hydroelectric dams have been built there in 2012. She discovered no longer a single fish may presumably bypass the dams. As a consequence, the dorado population has drastically declined in the headwaters of the Madeira in Bolivia, her research presentations.

Factual the origin

The Convention of Migratory Species maintains two lists: one for species threatened with extinction, and a 2nd for species that transfer across national borders and rely on international cooperation for his or her survival. The 2 goliath catfish, which are no longer yet at risk of going extinct, have been added to the 2nd list.

Scientists have called for global “swimways,” love animal-migration corridors on land, that would provide protection to key migratory fish habitats. Barthem and others also hope extra migratory fishes will gain listing under the convention, with almost 900 species making at least partial migrations in original water, the criteria for such an inclusion. (Read extra about how scientists are saving megafishes.)

Barthem, who was instrumental in mapping the epic dorado migration, adds original technologies will carry original insights to learning Amazonian fishes’ amazing journeys.

“We are legal starting to understand these migrations,” he says.