As you can imagine from the image below, the geographic range of this fish is smaller than other wild vertebrates. They are only found in the limestone caverns of the geothermal Devils Hole pool in Death Valley, Nevada. The pool is 3m wide, 20m long, 426 feet deep, and a very warm 92-93 degrees Fahrenheit. It is thought to have formed more than 500,000 years ago with the pupfish moving in around 50,000 years ago likely as a result of the roof of the cavern collapsing thereby exposing the cavern to surface water. In 2013 the tiny one-inch fish came close to extinction as there were only 35 observable fish in the pool. Although numbers have improved, the Devils Hole pupfish remains critically endangered.
In response, the U.S. Fish and Wildlife Service opened the Ash Meadows Fish Conservation Facility near Devils Hole. Here they are trying to establish a captive breeding program by transplanting pupfish eggs to the facility as adults do not seem to fare as well. According to Dr. Steven Beissinger at UC Berkeley, the pupfish has a 28-32% risk of extinction in the next 20 years. Contributing factors to their decline include warming water (as they already live near the upper limit for fish) as well as dwindling food supplies, genetic diversity, and loss of groundwater to meet agricultural needs. In fact, the U.S. Supreme Court ruled in favor of the pupfish in 1976 and limited groundwater pumping to maintain minimum water levels.
Conservationists have high hopes for the current captive breeding program as the fish mature quickly and are able to produce offspring multiple times within their first year of life.
Dr. Beissinger was quoted in a press release from Berkeley stating, “Somehow, this handsome little fish has heroically persisted in the harsh desert environment through thousands of years of drastic climate warming and droughts. Should the human condition ever arrive at this point after another century of increasing carbon dioxide emissions and climate warming, we may need someone to help us out of our hole.”