A new species of arapaima — a giant freshwater fish capable of breathing air with rudimentary lungs — has been found in the remote reaches of the Amazon River, and more distinct arapaima species may be discovered soon.

Capable of growing to 10 feet long and weighing upwards of 400 pounds, the heavily-armored fish lives in oxygen-poor waters and surfaces to breathe.

The arapaima is difficult to catch and study and is also endangered, which is why species classification is so important: Only about 5,000 of the fish still live in the wild.

It is “hard to argue for conservation if you don’t know it’s there,” explains Donald J. Stewart, a New York biology professor and National Geographic explorer whose team identified the new species. …