Owens Pupfish

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.

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.

Threats to the six populations include the encroachment of cattails into the waterways. The plant clogs the habitat and collects detritus, which eliminates the pupfish's breeding substrates. The CDFG tends the four populations, clearing out the cattails. Introduced species of aquatic organisms also pose a threat. They include predatory fish such as largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieu), brown trout (Salmo trutta), and bluegill (Lepomis macrochirus), as well as crayfish (Pacifastacus leniusculus) and bullfrogs (Rana catesbeiana). The severe reduction of the species into a single small population may have created a genetic bottleneck; genetic analysis is underway.

Other local Cyprinodon include Death Valley pupfish (Cyprinodon salinus salinus), Shoshone pupfish (Cyprinodon nevadensis shoshone), the extinct Tecopa pupfish (Cyprinodon nevadensis calidae), Devils Hole pupfish (Cyprinodon diabolis), and the desert pupfish (Cyprinodon macularius).