The numbers of arapaima, the Amazon River's largest fish, is quickly dwindling and can no longer be found in some areas of the Amazon basin.

In fact, the fish, commonly known as piracuru, is known for its ability to breathe in air. The ability to breathe air is both a blessing and a curse for the arapaima.

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Breathing air allows it to survive oxygen-poor water environments, but also makes it easier to catch. Arapaima spawning on the edge of floodplain forests gulp in air every 5 to 15 minutes, allowing local fishermen to find and harpoon them.

Weighing more than 400 pounds and measuring up to 10 feet, arapaima is a sought-after local food source. Local fishermen continue to fish for it even in areas with very low arapaima populations.

With some communities realizing the depletion of this food source, many fishermen have decided to "fish-down," meaning to catch smaller fish. This method, however, continues to be detrimental to the arapaima's existence.

Instead of using harpoons, fishermen use nets to catch smaller fish. In the process, they also catch young arapaima fish.

Despite the grim reality of fishing-down and overfishing, researchers have discovered that in areas where arapaima fishing is regulated, the giant fish is thriving. This gives scientists hope that by protecting the arapaima, the species might once regain its ecological foothold.

"The time has come to apply fishers' ecological knowledge to assess populations, document practices and trends, and solve fisheries problems through user participation in management and conservation," said Leandro Castella, lead scientist of the study and assistant professor of fisheries at Virginia Tech's College of Natural Resources and Environment.

An interesting and peculiar feature of the arapaima is its primitive lung that allows it to breathe air on the surface. Its gills allow it to breathe underwater.

The fish developed this unusual ability because it typically lives in waterways that don't have much oxygen.