Cyprinodon radiosus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Cyprinodon radiosus
Species Authority: Miller, 1948
Common Name(s):
English Owens Pupfish

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v) ver 3.1
Year Published: 2013
Date Assessed: 2011-11-22
Assessor(s): NatureServe
Reviewer(s): Smith, K. & Darwall, W.R.T.
Facilitator/Compiler(s): Hammerson, G.A. & Ormes, M.
This species is listed as Endangered because its extent of occurrence is less than 250 sq km, area of occupancy is less than 10 sq km, the species occurs in only 5 locations, and is subject to declines and local extirpations in the absence of frequent management.
2010 Endangered
1996 Endangered

Geographic Range [top]

Range Description: This pupfish is endemic to the Owens Valley, California, from Fish Slough and its springs (Mono County) near Bishop downstream to Owens Lake (Inyo County), including springs around the lake (Moyle 2002). It is now confined to several special refuges in the Owens Valley (Bolster 1990, Moyle 2002), including three in Fish Slough (Pond D, BLM Spring, and Marvin's Marsh), Warm Springs, and Well 368.
United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species is represented by five occurrences (subpopulations). As of the early 2000s, the species was regarded as stable in only two refuges (Moyle 2002).

Adult population size is unknown.

See Minckley et al. (1991) for a fairly detailed account of the historical status of this species.

USFWS (1990) categorized the status as "stable." As of the early 2000s, populations were regarded as stable in two refuges, but they remained threatened because they require active, ongoing management to keep the habitat favourable for pupfishes and to keep out alien species (Moyle 2002).
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: This pupfish was once abundant in shallow, clear, warm (about 10-25 °C) sloughs, spring pools, irrigation ditches, marshes with emergent bulrushes and Chara mats, and flooded pastures along the Owens River (Lee et al. 1980, Moyle 2002). Now it occurs mostly in deep pools and shallows of artificially created refugia (Bolster 1990). It needs good quality water, aquatic vegetation, and a silt- or sand-covered bottom. Males establish spawning territories in open areas close to shore; females stay in vegetation and emerge only to spawn; spawning substrate includes silty bottoms, submerged plants, algal clumps, rocks, or crevices, at depths up to 2 meters (Moyle 2002). Larvae and juveniles stay close to the substrate (Moyle 2002).
Systems: Freshwater

Use and Trade [top]

Use and Trade: This species is of minor value in commercial aquaria.

Threats [top]

Major Threat(s): Population decline was due to water diversion for agricultural and municipal uses and subsequent habitat alteration (loss of seasonally flooded shallows along the Owens River), and competition with and predation by introduced species. Current threats include introduced species (Largemouth Bass [which eliminated pupfish from the Owens Valley Native Fishes Sanctuary and BLM Spring; Moyle 2002], Mosquitofish, bullfrogs, crayfish), encroaching vegetation (cattails, tules, and other emergent plants), and vandalism. All populations are in small, artificial situations, vulnerable to stochastic fluctuations.

Conservation Actions [top]

Conservation Actions: Attempts to eliminate introduced fishes and crayfish should be continued, though efforts in the past have been unnsuccessful. Excessive growth of aquatic vegetation may need management. Livestock should be excluded from habitat. Fish barriers, water levels, and water flow need to be maintained (see Bolster 1990 for further details).

See recovery plan: Taylor and Williams (1984).

Most localities are being monitored by federal and state agency personnel (Bolster 1990).

Efforts to find suitable introduction sites should be continued.

Recovery plan calls for protection of five populations, each with at least 500 overwintering individuals; each populations should be well protected from any threats.

Citation: NatureServe 2013. Cyprinodon radiosus. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 30 August 2015.
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