Cyprinodon radiosus
Cyprinodon radiosus
(Owens Pupfish)
Fishes
Native Transplant
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Cyprinodon radiosus Miller, 1948
Common name: Owens Pupfish
Taxonomy: available through www.itis.govITIS logo

Identification: Moyle (1976a); Page and Burr (1991).
Size: 7.2 cm.
Native Range: Owens River system in Owens Valley, California, from the springs at Fish Slough in Mono County, to (but not in), Owens Lake, Inyo County, and in the springs around the lake. Currently only found naturally in the Owens Valley Native Fish Sanctuary and in BLM Spring in Fish Slough, a tributary of the Owens River, just north of Bishop (Miller 1968; Miller and Pister 1971; U.S. Fish and Wildlife Service 1984c).
Native range data for this species provided in part by NatureServe NS logo
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Cyprinodon radiosus are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA198419841Crowley Lake

Table last updated 3/30/2025

† Populations may not be currently present.
Means of Introduction: Intentionally stocked to create an additional population of this endangered species where the pupfish could survive without danger of extermination by predatory, nonindigenous fishes or further threatened by competition with introduced mosquitofish (Miller 1968). According to Miller (1968), this site was also intended to study the interspecific relationships among various fishes native to the Owens Valley. The Warm Springs refuge was created in 1970 under the supervision of the California Department of Fish and Game (Miller 1968) and presumably stocked soon afterwards.
Status: Established at Warm Springs, California (U.S. Fish and Wildlife Service 1984c).
Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.
Remarks: This pupfish is listed as a federally endangered species (Page and Burr 1991; U.S. Fish and Wildlife Service 1993a). The Warm Springs refugium is a small pond formed by a small dam and fed by a thermal spring located just outside of what is considered the species' native range (U.S. Fish and Wildlife Service 1984c). At least two populations of this species also survive as result of reintroductions made in 1969 and 1970 into sites within its historical range within the Owens River Valley near Bishop, California; both are in or adjacent to Fish Slough, one at the Owens Valley Native Fish Sanctuary and the other at the BLM Spring refugium (Miller 1968; U.S. Fish and Wildlife Service 1984c; Minckley et al. 1991). Minckley et al. (1991) reported that the California Department of Fish and Game stocked six other potential sites after about 1986, and that the species has survived in at least two of these sites. However, Minckley and his colleagues did not provide details on the site locations; thus it is not known if any of these stockings represent true introductions as opposed to reintroductions. Introduction of nonindigenous species has contributed to the Owen pupfish's decline (e.g., Miller 1968). Species introduced into the Owens River include largemouth bass Micropterus salmoides, brown trout Salmo trutta, mosquitofish Gambusia affinis, and crayfish Procambarus clarki. The largemouth bass, brown trout, and crayfish prey on adults. Mosquitofish probably compete with the Owens Pupfish for food and space and may prey on juveniles. Crayfish also prey on pupfish eggs (U.S. Fish and Wildlife Service 1993a). Creation of the various refugia typically involved elimination of nonindigenous species and erection of fish barriers preventing access to the site by nonindigenous predators, particularly largemouth bass (Miller 1968; Minckley et al. 1991).
References: (click for full references)

Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

U.S. Fish and Wildlife Service. 1984c. Recovery plan for the Owens pupfish, Cyprinodon radiosus. U.S. Fish and Wildlife Service, Portland, OR. 47 pp.

U.S. Fish and Wildlife Service. 1993a. Endangered and threatened wildlife and plants. 50 CFR 17.11 & 17.12. Federal Register, August 23, 1993. U.S. Department of the Interior, Washington, DC. 40 pp.

Williams, J. E., D. W. Sada, C. D. Williams, and other members of the Western Division of Endangered Species Committee. 1988. American Fisheries Society guidelines for introductions of threatened and endangered fishes. Fisheries 13(5):5-11.

Other Resources:
FishBase Summary
Author: Fuller, P.
Revision Date: 5/7/2019
Peer Review Date: 9/22/1999

Citation Information:
Fuller, P., 2025, Cyprinodon radiosus Miller, 1948: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=659, Revision Date: 5/7/2019, Peer Review Date: 9/22/1999, Access Date: 3/30/2025

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

Disclaimer:

The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2025]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [3/30/2025].

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Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.



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