Gambusia georgei 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Cyprinodontiformes Poeciliidae

Scientific Name: Gambusia georgei
Species Authority: Hubbs & Peden, 1969
Common Name(s):
English San Marcos Gambusia

Assessment Information [top]

Red List Category & Criteria: Extinct ver 3.1
Year Published: 2013
Date Assessed: 2012-02-03
Assessor(s): NatureServe
Reviewer(s): Smith, K. & Darwall, W.R.T.
Facilitator/Compiler(s): Hammerson, G.A. & Ormes, M.
This species is listed as Extinct because no genetically pure individuals have been found since 1983.
Previously published Red List assessments:
1996 Extinct (EX)
1994 Extinct (Ex)
1990 Extinct (Ex)
1988 Extinct? (Ex?)
1986 Endangered (E)

Geographic Range [top]

Range Description: Its historical range included the San Marcos Spring and upper few kilometres of the San Marcos River, Texas (Hubbs and Peden 1969, Page and Burr 2011).
Countries occurrence:
Regionally extinct:
United States (Texas)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: No occurrences are extant.

Population in 1969 was estimated at less than 1,000 individuals; genetically pure individuals have not been collected since 1983 (Johnson and Hubbs 1989); presumed extinct (Miller et al. 1989, USFWS 1990).
Additional data:

Habitat and Ecology [top]

Habitat and Ecology: Historical habitat included a large vegetated spring and its effluent (Page and Burr 2011); shallow, quiet, mud-bottomed, shoreline areas without dense vegetation in the thermally constant main channel. Formerly this species was common under the shade of bridges. Primary habitat requirements appear to be clean, clear water of a relatively stable temperature (Matthews and Moseley 1990).
Systems: Freshwater
Movement patterns: Not a Migrant

Threats [top]

Major Threat(s): Decline was due to reduced spring flows and pollution, including herbicide spraying along the river; introduced fishes; spread of an ornamental plant (Elephant Ears, Colocasia esculenta); and, as it became rare, hybridization with Gambusia affinis (Miller et al. 1989).

Conservation Actions [top]

Conservation Actions: This species is extinct and does not require protection or management, monitoring, or research action.

Citation: NatureServe. 2013. Gambusia georgei. The IUCN Red List of Threatened Species 2013: e.T8891A18233501. . Downloaded on 30 November 2015.
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