The Desert Hole Pupfish is a rare breed, actually on the endangered species list. It has been described as the world’s rarest fish, with a population of fewer than 200 since 2005.Genetic analysis indicates that the species evolved at the same time the cavern opened up to the surface, about 60,000 years ago. We visited the warm waters where it lives, just east of Death Valley National Park. The warm spring water is 93 degrees, and this fish lives in water up to 110 degrees! It is amazing to be traveling in the desert, and find a marsh with warm water, and then to visit the famous Desert Hole. The Devils Hole pupfish have been isolated 10,000 to 20,000 years, longer than any other in the Death Valley system. Devils Hole itself is a water-filled cavern cut into the side of a hill. The cavern is over 500 feet deep and the bottom has never been mapped. It is completely fenced in, and you view it from a walkway observation. To see pupfish up close, there is nice boardwalk in Ash Meadows National Wildlife Refuge that lets you get up close to the warm waters. The water is crystal clear, the the little male pupfish turn blue during mating time. Usually they are a silvery color and full-size is 2.5 inches, and their average lifespan is about 9 months. Here is a short video I filmed with a gopro underwater.