The dorado catfish is the all-time champion of freshwater fish migration, an international study has proven.

Known for its shimmering and scale-less silver-gold skin, the 6-foot-long dorado catfish (Brachyplatystoma rousseauxii) swims in the freshwaters of the Amazon River.

It has long been suspected that this species can achieve great feats of migration. Now, researchers from the Wildlife Conservation Society has confirmed that the dorado catfish can swim to great lengths that span the entire width of South America.

Epic Life Cycle Journey

In the study, researchers from the WCS's Amazon Waters Initiative investigated the dorado catfish and three goliath catfish species that reproduce in the river's western headwaters.

The dorado catfish and these related species are widely-dispersed in the basin of the Amazon and are among the most commercialized species.

Scientists discovered that the journey of the dorado catfish begins with pre-adults and adults traveling thousands of miles upriver of the Amazon estuary to spreading out in areas near the Andes mountains.

The breeding fish do not return to the nursery, but the newborn fish do, swimming thousands of miles in the opposite direction to complete the cycle. In fact, these fish complete a life-cycle migration of about 7,200 miles (11,600 kilometers).

"This is the first time that scientific research has linked the full range of these fish species," said Ronaldo Barthem, lead author of the paper.

To confirm their findings, Barthem and his colleagues mapped the long-distance migratory movements of the dorado catfish, as well as its goliath catfish cousins: B. platynemum, B. vaillantii, and B. juruense.

Results reveal that adult dorado catfish swimming upstream from the Amazon River estuary may take about one to two years to reach the spawning grounds in the Andes. Researchers also found that two of the goliath catfish (B. juruense and B. platynemum) also spawn in or near the Andes foothills.

Freshwater Fish Conservation

Michael Goulding, an aquatic scientist and Barthem's co-author, said the headwater infrastructure development in the Andes is one of the biggest threats to the dorado catfish and other freshwater fish species in the region. He said the developments could heavily affect the spawning grounds of these freshwater migrants.

Furthermore, Goulding said many questions still remain about the dorado catfish and the goliath catfish, such as why these species travel so far to reproduce and why they go back to the breeding place to respawn.

"Now we have a baseline that will help direct the trajectory of future research and conservation efforts," added Goulding.

Details of the study are featured in the journal Scientific Reports.

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