Common name: Gila Topminnow
Synonyms and Other Names: Gila topminnow, Yaqui topminnow
available through www.itis.gov
Identification: Poeciliopsis occidentalis occidentalis a small live-bearing fish that exhibits sexual dimorphism. Both males and females having a tan to olive colored body and usually white on the belly. Scales of the dorsum are darkly outlined and the fin rays contain melanophores (pigment-containing and light-reflecting cells), although lacking in dark spots. Males in breeding color are black with orange at the base of the gonopodium (modified anal fin used to fertilize the female internally), and have bright yellow pelvic, pectoral, and caudal fins (Minckley 1973).
There are two listed subspecies of the Sonoran topminnow (P. occidentalis); the Gila topminnow (P. o.occidentalis) of the Gila River basin and the Yaqui topminnow (P.o. sonoriensis) of the Rio Yaqui. Both subspecies were listed as endangered within the U.S. portion of their range in 1967 with no critical habitat designation. (U.S. Fish and Wildlife Service 1998).
Size: Females grow to 5 cm standard length (SL); males to about 2.5 cm SL (U.S. Fish and Wildlife Service 1998)
Native Range: Poeciliopsis occidentalis occidentalis is endemic to Gila River system of Arizona, New Mexico, and northern Sonora, Mexico and the Yaqui River system in southeastern Arizona and northern Mexico (U.S. Fish and Wildlife Service 1983). Now extirpated in New Mexico and rare in Arizona (Page and Burr 1991).
Hydrologic Unit Codes (HUCs) Explained
Puerto Rico &
Interactive maps: Point Distribution Maps
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 Poeciliopsis occidentalis occidentalis are found here.
Table last updated 8/2/2021
† Populations may not be currently present.
Ecology: Poeciliopsis occidentalis occidentalis prefers shallow, warm springs or slow-moving waters, but can tolerate a wide range of temperature and current regimes. Primarily omnivorous, consuming detritus, algae, amphipods, ostracods, and insect larvae. Generally only lives one year, with sexual maturity occuring as soon as two months. Viviparous, similar to other topminnows, with breeding occuring January through August (U.S. Fish and Wildlife Service 1998).
Means of Introduction: This endangered species was intentionally stocked to create additional populations. It was introduced into Arivaca Creek in 1936. Populations were abundant by 1957, but were extirpated in less than two years by introduced mosquitofish (U.S. Fish and Wildlife Service 1983). The species is established in Hidden Waters, where it was first stocked in 1976. It was stocked in Tule Creek in 1968, but extirpated by flooding in 1978. It was restocked in October 1981 and was still established as of 1983. The fish first was stocked at Seven Springs and Cave Creek in the late 1960s, but the population was lost to flooding several times. It was restocked in 1975, but extirpated by flooding again in 1978. It was stocked again in February 1980 and became established. It was stocked in Cow Creek in September 1981 and became established (U.S. Fish and Wildlife Service 1983). Simons (1987) documented more than a hundred introductions of Poeciliopsis o. occidentalis into isolated Arizona waters, many of which were created for livestock watering and therefore, were historically fishless.
Status: Most stocked populations have failed or were extirpated; however, several stocked locations still have extant populations.
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.
References: (click for full references)
Dawes, J.A. 1991. Livebearing fishes. A guide to their aquarium care, biology and classification. Blandforn, London, England.
Duncan, D. - U.S. Fish and Wildlife Service (pers. communication)
Johnson, J. E. 1970. A New Locality for the Gila Topminnow, Poeciliopsis Occidentalis (Poeciliidae) The Southwestern Naturalist, 14(3): 368.
Minckley, W.L. 1969. Attempted re-establishment of the Gila topminnow within its former range. Copeia 1969:193-194
Minckley W.L. 1973. Fishes of Arizona. Arizona Game and Fish Department, Phoenix, AZ.
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.
Simons, L.H. 1987. Status of the Gila topminnow (Poeciliopsis o. occidentalis) in the United States. Special report on Project E-1, title VI of the Endangered Species Act of 1973, Arizona Game and Fish Department, Phoenix, AZ.
Sublette, J.E., M.D. Hatch, and M. Sublette. 1990. The fishes of New Mexico. New Mexico Department of Game and Fish, University of New Mexico Press, Albuquerque, NM.
U.S. Fish and Wildlife Service. 1983. Gila and Yaqui topminnow recovery plan. U.S. Fish and Wildlife Service, Albuquerque, NM.
U.S. Fish and Wildlife Service. 1994. Yaqui fishes recovery plan. U.S. Fish and Wildlife Service, Albuquerque, NM.
U.S. Fish and Wildlife Service. 1998. Gila topminnow, Poeciliopsis occidentalis occidentalis, revised recovery plan. U.S. Fish and Wildlife Service, Albuquerque, NM.
Wischnath, L. 1983. Atlas of livebearers of the world. TFH Publications, Inc., Neptune, NJ.
Nico, L., Fuller, P., Neilson, M., and Daniel, W.
Revision Date: 6/13/2019
Peer Review Date: 6/13/2019
Nico, L., Fuller, P., Neilson, M., and Daniel, W., 2021, Poeciliopsis occidentalis occidentalis (Baird and Girard, 1853): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=866, Revision Date: 6/13/2019, Peer Review Date: 6/13/2019, Access Date: 8/2/2021
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.