Can you imagine living in a hole somewhere in the middle of nowhere? The Devil’s Hole pupfish, appropriately named for the small water-filled hole they live in, is known as the critically endangered rarest fish in the world. The merely inch-long fish boasts sparkling blue scales and an extremely dangerous environment. 

      The fish’s habitat is specifically only the small surface of an aquifer entrance in Ash Meadows National Wildlife Refuge in the Mojave Desert, Nevada. Despite the water depth extending far below where the fish are found, the species survives solely in the top 80 feet or less of the hole. The water itself remains 94 degrees and contains very low amounts of oxygen. Conditions like this would be deadly to most other species, but the Devil’s Hole pupfish seems to have no problem living in it. Yet, if the conditions are different the fish had trouble adapting, as scientists have tried and failed to make habitats for them outside their small hole. 

      The fish itself is related to a nearby species of pupfish, but is classified as unique. Its population wavers and fluctuates over years, puzzling scientists. In 2013, there were only 35 pupfish counted living in the hole. The population appears to be steadily decreasing slowly over time, recovering then decreasing more than before. Today, the population sits at 136, and researchers await the next count to see the future of such a small fish.

Source: Devil’s Hole Pupfish. Nevada Fish and Wildlife Office, fws.gov.