Measuring 10 feet (3 meters) long and weighing in at more than 400 pounds (180 kilograms), it's hard to imagine that the arapaima, the largest fish in the Amazon River basin, could ever go missing. But these huge fish are quickly disappearing from Brazilian waterways, according to a new study.

 

A recent survey of fishing communities in the state of Amazonas, Brazil, found that the arapaima is already extinct in some parts of the Amazon basin. In other parts of the Amazon, its numbers are rapidly dwindling.

 

However, the researchers also uncovered some good news: In communities where arapaima fishing is regulated, the species is actually thriving, giving the researchers hope that conservation of the species is still possible.

 

Commonly known as pirarucu, arapaima (Arapaima gigas) are the largest freshwater fish in South America. They're unique among fishes for their ability to breathe air — a feat made possible by a primitive lung, which they possess in conjunction with a gill system that allows them to breathe underwater. The fish developed this function because they typically live in oxygen-poor waterways, according to the Tennessee Aquarium, which is home to several arapaima.

 

But while this supplemental breathing technique helps the fish survive in its native habitat, it also makes the arapaima much easier to catch, according to the researchers.

 

"Arapaima spawn on the edges of floodplain forests and come to the surface to breathe every 5 to 15 minutes, when they are easily located and harpooned by fishers using homemade canoes," said Caroline Arantes, a doctoral student in wildlife and fisheries science at Texas A&M University in College Station, who helped conduct the study.