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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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Common name: Gila Topminnow

Synonyms and Other Names: Gila topminnow, Yaqui topminnow

Taxonomy: 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).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

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

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.

Remarks: Wischnath (1993) considered P. occidentalis to be the most attractive member of the genus. It is listed as federally endangered (U.S. Fish and Wildlife Service 1993). The Yaqui topminnow also has been stocked commonly in portions of Yaqui River system where it is native (U.S. Fish and Wildlife Service 1983, 1994). Likewise, Minckley (1969) listed locations within the natural range where reintroduction of the Gila topminnow was attempted. Both subspecies are affected by introduced western mosquitofish Gambusia affinis which prey on juvenile topminnows and harass adults (U.S. Fish and Wildlife Service 1983, 1994).

Species was stocked in several sites in Arizona within their native historical range, including Hidden Waters, a tributary of the Salt River; the Boyce Thompson Arboretum, near Superior, Pinal County; Seven Springs, a tributary to the Gila River; Tule Creek, a tributary to the Agua Fria River; Arivaca Creek; and Cow Creek, a tributary to the Agua Fria River (U.S. Fish and Wildlife Service 1983). Stocked populations at Hidden Waters and Arivaca Creek were extirpated because of introduction of nonnative fish and habitat alteration. Established at Tule Creek, Seven Springs, and Cow Creek (U.S. Fish and Wildlife Service 1983).

The recovery plan (1983) and draft revised recovery plan (1998) both consider the historic range of the topminnow broadly. Historic range for the Gila topminnow is considered to be the entire Gila River basin, below 4000 feet elevation. This includes subwatersheds with no historic collections such as the Hassayampa and Agua Fria Rivers. Releases of Gila topminnow in the Gila River Basin are considered to be reintroductions, even though there are no historic collections for a site. For various reasons, management and recovery of the fish requires this approach. The Desert Fishes Recovery Team approved the definition of historic range and the recovery approach (Doug Duncan, pers. communication).

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.

Other Resources:

Author: Nico, L., Fuller, P., Neilson, M., and Daniel, W.

Peer Review Date: 6/13/2019

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.