Video: Close-up of unique fish in the world at the

This small green fish is a unique species. They can live in harsh environments that are incompatible with fish.

Devils Hole pupfish is one of the rarest fish in the world , this fish lives in a lake located deep in the limestone cave called "Devil's Hole". The temperature in the pit is always 33 degrees Celsius and only a few miles from Death Valley National Park.

They often eat algae that live on the surface of the water, scientists estimate that the fish have lived in the cave for at least 60,000 years and they have been listed as endangered animals since 1967.

Devils Hole pupfish fish.

Scientists still do not know why the number of these fish species began to decline since 1990. They have repeatedly bred Devils Hole pupfish but failed.

Limestone caves have a depth of about 152 meters, but the depth of the reservoir has not been measured. In order to preserve this fish and not knowing the depth of the cave in the cave, the "Devil's Hole" closed without visitors.

Calculated in April of Death Valley National Park, there are only about 115 Devils Hole pupfish in the world.