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Giant catfish clocks longest ever freshwater migration

  • The dorado catfish uses the massive Amazon River as its roadway, beginning its journey at the river’s headwaters.
  • It spawns in the far western Amazon, then drifts thousands of miles towards the estuary in the opposite direction.
  • After two to three years in the estuary, the catfish makes its way back towards the headwaters through the Amazon floodplain.

An Amazonian catfish — the dorado catfish — makes the world’s longest known freshwater migration, a new study has confirmed.

Clocking more than 7,200 miles (~11,600 kilometers), the dorado catfish (Brachyplatystoma rousseauxii) travels nearly the entire width of the South America continent during its life cycle, breaking its own previous record, researchers report in the study published in Scientific Reports.

The marathon swimmer uses the massive Amazon River as its roadway, beginning its journey at the river’s headwaters. It spawns in the far western Amazon, in or near the Andes Mountains. The newborn dorado catfish larva, just a few centimeters long, then drifts thousands of miles towards the estuary in the opposite direction, where freshwater from the mouth of the Amazon River flows into the salty Atlantic ocean. This estuary is the fish’s nursery.

Map of the dorado catfish’s life-cycle migration through the Amazon River basin. Map courtesy of WCS.

After two to three years in the estuary, the dorado catfish, now larger in size, makes its way back towards the headwaters through the Amazon floodplain, feeding and growing in size along the way.  Once it reaches the spawning areas, the fish breeds, starting the cycle all over again. The newborn larvae swim towards the nursery areas, while the breeding catfish stay put. The round-trip stretches for more than 7,200 miles.

“Many questions remain about these incredible fish, such as why they travel so far to reproduce and do they return to place of birth to spawn,” Michael Goulding, aquatic scientist at the Wildlife Conservation Society (WCS), said in a statement. “Now we have a baseline that will help direct the trajectory of future research and conservation efforts.”

The dorado catfish and other closely related species known as goliath catfish are economically important species for the fishing industries in the Amazon River basin. Photo credit: Michael Goulding/WCS.

The dorado catfish, which can grow up to 3 meters in size, is important commercially. Migratory species like this catfish need a high degree of connectivity within the river system to maintain healthy populations. However, this connectivity is rapidly being lost due to the activities like construction of dams, mining and expansion of agriculture. Overfishing, too, is threatening the catfish’s survival in the wild.

“Of special relevance is the expected infrastructure development in the Andes, especially the combination of dams, headwater deforestation and mining activity, which could present major threats to important spawning areas ranging from Colombia in the north to Bolivia in the south,” the authors write in the paper. “The long-distance migratory goliath catfishes provide a profound biological indicator of ecosystem health from the Andes to the freshwater Amazon River plume in the Atlantic, and the impacts on them should be considered in all major infrastructure development.”

A live dorado catfish in a tank. Photo credit: Michael Goulding/WCS.

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