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.

Poecilia sphenops
Poecilia sphenops
(Mexican Molly)

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Poecilia sphenops Valenciennes in Cuvier and Valenciennes, 1846

Common name: Mexican Molly

Synonyms and Other Names: (liberty molly).

Taxonomy: available through www.itis.govITIS logo

Identification: Distinguishing characteristics were given by Miller (1983). However, there appers to be a good deal of confusion among species of shortfin mollies in the literature. Miller (1983) provided a key to this species and other Poecilia found in Mexico. Photographs or illustrations appeared in Schultz and Miller (1971), Mills and Vevers (1982), Axelrod et al. (1985), Petrovicky (1988), Dawes (1991), Sakurai et al. (1993), and Wischnath (1993). This species is part of the P. sphenops complex (Rosen and Bailey 1963; Schultz and Miller 1971; Brett and Turner 1983; Miller 1983). Formerly known as Mollienesia sphenops.

Size: 10 cm TL, but commonly smaller.

Native Range: Atlantic Slope of eastern Mexico from north of Veracruz City to Guatemala (Brett and Turner 1983; Miller 1983). Some authors state it ranges south to Colombia (Wischnath 1993) but that may be the result of taxonomic confusion.

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 Poecilia sphenops are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AZ198019801Lower Gila-Painted Rock Reservoir
CA198019802Salton Sea; Santa Ana
FL197420192South Atlantic-Gulf Region; Tampa Bay
NV196720206Lake Mead; Las Vegas Wash; Lower Virgin; Meadow Valley Wash; Muddy; White
PR200720213Cibuco-Guajataca; Eastern Puerto Rico; Southern Puerto Rico

Table last updated 4/22/2024

† Populations may not be currently present.

Means of Introduction: Introductions have resulted from escapes, intentional releases from fish farms, and releases by aquarists (Lee et al. 1980 et seq.; Dill and Cordone 1997).

Status: Locally established in Montana and Nevada: failed in Florida; reported from California and Arizona. Established in Puerto Rico.

Impact of Introduction: Introduced populations have adversely affected the Moapa dace Moapa coriacea and the White River springfish Crenichthys baileyi (both endangered species) and are a potential threat to other native fishes in the Pahranagat Valley, Nevada (Lee et al. 1980 et seq.). Scoppettone (1993) attributed the effects on the Moapa dace to be caused by P. mexicana, so the question of identity is raised again.

Remarks: Some, conceivably all, of the records of this species in the United States may turn out to represent one of the other members of the P. sphenops species complex and not P. sphenops. For instance, the Hawaiian records of P. sphenops (Maciolek 1984) and that of P. mexicana (Devick 1991) are now considered the same fish (Poecilia sp.; Mundy 2005). Similarly, Schoenherr (1979) reported taking P. sphenops from a canal northwest of the Salton Sea in California; however, according to Dill and Cordone (1997), later authors questioned the identification and therefore did not include P. sphenops in their listings of California fishes (e.g., Hubbs et al. 1979; Shapovalov et al. 1981). At least five members of the P. sphenops species complex have been reported from the United States (Courtenay and Hensley 1979).

There are 2 voucher specimens from Hawaii from a 1976 collection on Oahu (USNM 247410.5105873).

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.

Brett, B.L.H. and B.L. Turner. 1983. Genetic Divergence in the Poecilia sphenops complex in Middle America. Systematics and Ecology 11: 127-137.

Courtenay, W.R., Jr., and D.A. Hensley. 1979. Survey of introduced non-native fishes. Phase I Report. Introduced exotic fishes in North America: status 1979. Report submitted to National Fishery Research Laboratory, U.S. Fish and Wildlife Service, Gainesville, FL.

Courtenay, W.R., Jr., H.F. Sahlman, W.W. Miley, II, and D.J. Herrema. 1974. Exotic fishes in fresh and brackish waters of Florida. Biological Conservation 6(4):292-302.

Dawes, J.A. 1991. Livebearing fishes. A guide to their aquarium care, biology, and classification. Blandford Press, London, England.

Devick, W. S. 1991. Patterns of introductions of aquatic organisms to Hawaiian freshwater habitats. Pages 189-213 in new directions in research, management and conservation of Hawaiian freshwater stream ecosystems. Proceedings of the 1990 symposium on freshwater stream biology and fisheries management, Division of Aquatic Resources, Hawaii Department of Land and Natural Resources.

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.

Grana, F. - Puerto Rico Department of Natural and Environmental Resources, San Juan, PR.

Hubbs, C.L., W.I. Follett, and L.J. Dempster. 1979. List of the fishes of California. California Academy Science Occasional Papers 133:1-51.

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980 et seq. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, NC.

Maciolek, J.A. 1984. Exotic fishes in Hawaii and other islands of Oceania. 131-161 in W.R. Courtenay, Jr., and J.R. Stauffer, Jr., editors. Distribution, biology, and management of exotic fishes. The Johns Hopkins University Press, Baltimore, MD.

Miller, R.R. 1983. Checklist and key to the mollies of Mexico (Pisces: Poecilidae, Poecilia, subgenus Mollienesia) Copeia 1983(3):817-822.

Mills, D., and G. Vevers. 1982. The Golden encyclopedia of freshwater tropical aquarium fishes. Golden Press, Racine, WI.

Mundy, B.C.  2005.  Fishes of the Hawaiian Archipelago.  Bishop Museum Bulletins in Zoology, Number 6.

Petrovicky, I. 1988. Aquarium fish of the world. Hamlyn, London, England.

Rosen, D.E., and R.M. Bailey. 1963. The poeciliid fishes (Cyprinodontiformes), their structure, zoogeography, and systematics. Bulletin of the American Museum of Natural History 126:1-176.

Sakurai, A., Y. Sakamoto, and F. Mori. 1993. Aquarium fish of the world: the comprehensive guide to 650 species. Chronicle Books, San Francisco, CA.

Schoenherr, A A. 1979. Niche separation within a population of freshwater fishes in an irrigation drain near the Salton Sea, California. Bulletin of the Southern California Academy of Science 78(1):46-55.

Schultz R.J., and R.R. Miller. 1971. Species of the Poecilia sphenops complex (Pisces: Poeciliidae) in Mexico. Copeia 1971(2):282-290.

Scoppettone, G.G. 1993. Interactions between native and nonnative fishes of the upper Muddy River, Nevada. Transactions of the American Fisheries Society 122(4): 599-608.

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

St. Amant, J.A., and F.G. Hoover. 1969. Addition of Misgurnus anguillicaudatus (Cantor) to the California fauna. California Fish and Game 57(2):330-331.

Wischnath, L. 1993. Atlas of livebearers of the world. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

FishBase Summary

Author: Leo Nico, Pamela J. Schofield, Matt Neilson, and Bill Loftus

Revision Date: 9/17/2012

Peer Review Date: 9/17/2012

Citation Information:
Leo Nico, Pamela J. Schofield, Matt Neilson, and Bill Loftus, 2024, Poecilia sphenops Valenciennes in Cuvier and Valenciennes, 1846: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=864, Revision Date: 9/17/2012, Peer Review Date: 9/17/2012, Access Date: 4/22/2024

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. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [4/22/2024].

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