Giant air-breathing fish found in the Amazon

A new species of the mysterious arapaima has been discovered in the remote backwaters of the Amazon.

Measuring up to 10ft long and weighing up to 440 pounds, the arapaima has long remained something of an enigma. Found within the oxygen-depleted backwaters of South America, this monster of the rainforest breathes air through a primitive lung and has managed to evade study thanks to its remote location and the fact that it is quite a difficult fish to catch.

Up until now the arapaimas found in the Amazon have been thought to belong to the same species, albeit with regional variations. According to National Geographic explorer Donald J. Stewart and colleagues however, there could actually be several species - many of them undiscovered.

Their findings were based on a specimen collected in 2001 which has turned out to be a distinctly different species to most of the arapaimas caught in the region.

"I think we'll have many more species before we're done," said Stewart.

While the discovery is good news for biologists, it also means that some of these elusive fish may be a lot more endangered than previously believed.

These days it is illegal to catch arapaimas and there are thought to be only around 5,000 left.

If this population consists of several different species, then it means that many of those are going to be a lot more endangered and some could even be on the brink of extinction.

"We need to pay attention to this diversity so we don't eliminate one of them," said Stewart.