Due to the fear of extinction in the 1960s and 1970s, several measures were taken to create multiple populations of the pupfish outside of Devils Hole to safeguard the species, which is known as "ex situ" conservation. Some of these measures, such as transplanting the fish into nearby natural springs, quickly failed. The fish disappeared, though one population at Purgatory Spring was destroyed by biologists, as the fish were misshapen and no longer looked like Devils Hole pupfish. Two attempts were made at this time to establish aquaria populations, one at Steinhardt Aquarium and the other at Fresno State College, though these also failed. A number of artificial "refugia" consisting of concrete tanks approximating conditions in Devils Hole were attempted to ensure the species' survival should the natural population at Devils Hole die out. The Hoover Dam Refugium for Endangered Desert Fish was established in August 1972, with the first twenty-seven pupfish translocated in October 1972. The Hoover Dam Refugium was successfully maintained for several years and reached a population of several hundred, though the sex ratio was highly skewed towards males with as many as three males per female. In 1985 or 1986, a component of the water supply system failed, however, killing many of the fish. Nearly all the remaining fish were killed by October 1986 when an additional failure caused the water temperature to drop drastically. The lone surviving fish was then removed. In 1973, a second refugium was established at Ash Meadows National Wildlife Refuge (AMNWR), the Amargosa Pupfish Station, also known as the School Springs refuge. From the founding population of twenty-five fish, it remained at several dozen individuals until a power failure in August 1984 disrupted the water flow, reducing the population to seven. The population increased to 121 by October 1987. In 1990, a third refugium was constructed, also at AMNWR, called Point of Rocks refuge.