The Owens pupfish (Cyprinodon radiosus) is a rare species of fish in the family Cyprinodontidae, the pupfish. It is endemic to California in the United States, where it is limited to the Owens Valley. It is a federally listed endangered species of the United States. This pupfish is up to 5 centimetres (2.0 inches) long, the largest males sometimes longer. The male is blue-gray, turning bright blue during spawning. The female is greenish brown with a silvery or whitish belly.

Ecology and Behavior

The pupfish tolerates a wide range of water conditions. Its native habitat includes desert marshes with water temperatures up to 33 °C in the summer and layers of ice during the winter. The water in some areas has four times the salt content of the ocean, as well as low oxygen.

Typically, species in the genus Cyprinodon reproduce ranging from May to September, with the season peaking in June and July in particular. There are territorial, satellite, and sneaker types of male mating behavior. Females can lay 10 eggs daily on average for multiple times during the reproductive season. However, pupfish have a very short reproductive cycle in April. When captured during the summer, both male and female fish were not in breeding season and died out within days despite being placed in the spring water they are used to living in.

This fish was once common in the Owens Valley of California, occurring in most water bodies between Fish Slough and Lone Pine, which are 70 miles apart. The bodies of water are shallow, up to 3 feet in depth, and have a temperature between 18 and 20 degrees Celsius. It occurred in the Owens River and associated sloughs and marshes. At that time the Paiute people scooped them out of the water and dried them for the winter.

Recovery Efforts

The diversion of water from the Owens River to the Los Angeles Metropolitan Area during the California Water Wars eliminated most of the water bodies that were the pupfish's habitat. Predation by introduced species of fish may have decimated remaining populations. By 1942 this pupfish was believed to be extinct. It was rediscovered in 1969, when one population of about 800 individuals was found. When they were transferred to a safer location by Phil Pister, a retired district fishery biologist, the entire global population of this pupfish was contained in two buckets. Since the pupfish were a fragile species, many of them died before making it to relocation in Fish Slough. The California Department of Fish and Game established six populations in carefully managed refuge using these fish. While not all of the original six populations still exist today, the CDFW is still protecting and maintaining the population. The Endangered Species Act of 1973 was later passed on to help with more direct recovery efforts for different species on a grander scale. In 2021, another population of Owens pupfish was established at the River Spring Lakes Ecological Reserve in Mono County, California. This brought the total number of populations back up to 6. To establish this new population, pupfish were sourced from the five other extant populations and translocated to the approximately 650-acre (264-hectare) reserve.

Evolutionary Research