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.

Nematolebias whitei
(Rio pearlfish)

Copyright Info
Nematolebias whitei (Myers, 1942)

Common name: Rio pearlfish

Synonyms and Other Names: White's pearlfish, Cynolebias whitei Myers 1942, Pterolebias elegans Ladiges 1958

Taxonomy: available through www.itis.govITIS logo

Identification: Costa (1995) provided diagnostic characters and included this species in his identification keys to the genera and species of the subfamily Cynolebiatinae. Color photographs appeared in Axelrod et al. (1985) and Costa (1995). This species, formerly known by the name Cynolebias whitei, was assigned to the genus Simpsonichthys by Costa (1996), and to the genus Nematolebias by Costa (1998).

Size: 9 cm.

Native Range: Tropical America. South America in the coastal plains of Rio de Janeiro State, between Rio das Ostras and Marica, southeastern Brazil (Costa, personal communication).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: This pearlfish has been listed as a nonestablished species known from open waters of California (Courtenay et al. 1986, 1991; Courtenay and Williams 1991; Williams and Jennings 1991). That listing likely based on its introduction into experimental rice plots and ponds on lands of the Butte County Mosquito Abatement District in 1973 and 1974 (e.g., Shapovalov et al. 1981; Dill and Cordone 1997), and at the Agricultural Experiment Station on the University of California Riverside (Dill and Cordone 1997).

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 Nematolebias whitei are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA196419732Butte Creek; Santa Ana

Table last updated 11/29/2023

† Populations may not be currently present.

Means of Introduction: Intentionally stocked to assess its ability as a mosquito control agent, especially in ricefields (Dill and Cordone 1997). These studies were with the approval of the Fish and Game Commission (Dill and Cordone 1997).

Status: Failed in California (Moyle 1976). As in the case of the black pearlfish Austrolebias nigripinnis, Dill and Cordone (1997) concluded that there is no evidence that this pearlfish species was ever an inhabitant of open waters (see Remarks section).

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: Like other annual killifishes, this species is capable of surviving in temporary pool habitats. Dill and Cordone (1997) gave details on the history of this species in California. It is essentially the same story as that of the blackfin pearlfish A. nigripinnis. Dill and Cordone argued that the ponds and rice paddies where these fish were released should not be considered open waters. Unfortunately, the literature does not provide details on the outflow connections, if any, of the experimental ponds or of the ricefield areas where this species was used. In addition, if these sites were subject to periodic flooding from adjacent areas, then the introductions may be considered open water. There are no known voucher specimens.

References: (click for full references)

Axelrod, H.R., W.E. Burgess, N. Pronek, and J.G. Walls. 1985. Dr. Axelrod's atlas of freshwater aquarium fishes. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Costa, W.J.E.M. 1995. Pearl kililfishes - the Cynolebiatinae: systematics and biogeography of the neotropical annual fish subfamily. T.E.H. Publications, Neptune City, NJ.

Costa, W.J.E.M. 1996. Phylogenetic and biogeographic analysis of the Neotropical annual fish genus Simpsonichthys (Cyprinodontiformes: Rivulidae). Journal of Comparative Biology 1:129-140

Costa, W.J.E.M. 1998. Phylogeny and classification of Rivulidae revisited: origin and evolution of annualism and miniaturization in rivulid fishes (Cyprinodontiformes: Aplocheiloidei). Journal of Comparative Biology 3:33-92.

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. 1986. Distribution of exotici fishes in North America. 675-698 in Hocutt, C.H., and E.O. Wiley, eds. The zoogeography of North American freshwater fishes. John Wiley and Sons. New York, NY.

Courtenay, W.R., Jr., D.P. Jennings, and J.D. Williams. 1991. Appendix 2: exotic fishes. 97-107 in Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. Common and scientific names of fishes from the United States and Canada, 5th edition. American Fisheries Society Special Publication 20. American Fisheries Society, Bethesda, MD.

Dill, W.A., and A.J. Cordone. 1997. History and status of introduced fishes in California, 1871-1996. California Department of Fish and Game Fish Bulletin, volume 178.

Moyle, P. B. 1976. Inland fishes of California. University of California Press, Berkeley, CA.

Shapovalov, L., A.J. Cordone, and W.A. Dill. 1981. A list of freshwater and anadromous fishes of California. California Fish ad Game 67(1):4-38.

Williams, J.D. and D.P. Jennings. 1991. Computerized data base for exotic fishes: the western United States. California Fish and Game 77(2):86-93.

FishBase Summary

Author: Leo Nico, and Matt Neilson

Revision Date: 4/30/2018

Peer Review Date: 3/1/2012

Citation Information:
Leo Nico, and Matt Neilson, 2023, Nematolebias whitei (Myers, 1942): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=882, Revision Date: 4/30/2018, Peer Review Date: 3/1/2012, Access Date: 11/29/2023

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.


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. [2023]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [11/29/2023].

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