San Marcos gambusia

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San Marcos gambusia
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Genus: Gambusia
G. georgei
Binomial name
Gambusia georgei
C. Hubbs & Peden, 1969

The San Marcos gambusia (Gambusia georgei) is an extinct species of gambusia that was found only in the San Marcos Springs of Central Texas. The fish has not been seen since 1983.


The San Marcos gambusia was typically less than 1.6 inches (4 cm) in length. It had a dark body with a slight blue tint, although the median fins were lemon yellow. The scales were strongly crosshatched, and the dorsal fin had a dark stripe along its edge. The species’ exact diet is not known, but other poeciliids typically eat insect larvae and other small invertebrates. The fish were live bearing, and have been known to give birth to a few dozen young at a time.[2]


Downstream from the headwaters of the San Marcos Springs, Aquarena Springs, and Spring Lake

The San Marcos gambusia has only been identified in a 0.6-mile (1-km) stretch of the headwaters of the San Marcos River. They appeared to need clean and clear water, with little temperature variability. They apparently also preferred shallow, quiet water, along with partial shade.[1]


As of 1969, the population was less than 1,000 Individuals. The species was threatened by reduced spring flows and pollution, including sprayed herbicide along the river and introduced fish (Gambusia affinis) and plants (Colocasia esculenta). As no specimens have been sighted since 1983, the species is now considered extinct.[1]


  1. ^ a b c NatureServe 2013 (2013). "Gambusai georgei". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 2 May 2015.
  2. ^ "Endangered Species of the Edwards Aquifer - Gambusia georgei". The Edwards Aquifer Website.

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