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    Gambusia georgei
    San Marcos Gambusia
    Credit: F. Douglas Martin

    Taxonomic Hierarchy

    Life
    Animalia
    Chordata
    Actinopterygii
    Cyprinodontiformes
    Poeciliidae (Livebearers)
    Gambusia
    Gambusia georgei (San Marcos Gambusia)

    Description

    All text below is derived from a January 2013 copy of Dr. Timothy Bonner's website at Texas State University. That content was derived primarily from published literature. We are aware of some conflicts with the museum record and the content below will evolve as the new, expanded UT and Texas State Fishes of Texas project team members are able to update it. We invite collaborations to improve and expand the species account content. Please contact us if you wish to help, or if you discover flaws in our species account content that you can address.

    Type Locality

    San Marcos River at Hwy. I-35 bridge, Hays County, Texas (Hubbs and Peden 1969).

     

    Etymology/Derivation of Scientific Name

     

     

    Synonymy

     

     

    Characters

    Maximum size: Adult size 25-40 mm SL (Guillory 1980).

     

    Coloration: Dark edges on dorsal and caudal fins; distinctly cross-hatched side; lemon yellow median fins (Page and Burr 1991). No dark bands on sides; median fins without large black spots near their bases (Hubbs et al. 2008).

     

    Counts:

     

    Body shape: Dorsal fin origin well behind anal fin origin (Hubbs et al. 2008).

     

    External morphology: Distal segments of anterior branch of 4th fin ray of gonopodium coalesced to elbow; spines at tip of 3rd anal fin ray of male gonopodium 4-10 times longer than wide (Hubbs et al. 2008).

     

    Internal morphology: Intestinal canal short with few convolutions (Hubbs et al. 2008).

     

    Distribution (Native and Introduced)

    U.S. distribution:

     

    Texas distribution: Restricted to a very limited portion of the San Marcos River springrun several kilometers below the headsprings (Hubbs et al. 2008).

     

    Abundance/Conservation status (Federal, State, NGO)

    Extinct (Hubbs et al. 2008); State Endangered (Texas); Federally Endangered; species has always been rare and its existence difficult to document (Hubbs et al. 2008). Listed as Possibly Extinct by the American Fisheries Society; categories of threats: present or threatened destruction, modification, or reduction of habitat or range; and a narrowly restricted range (Jelks et al. 2008). Extinct throughout range (Warren et al. 2000). Species likely extinct (Miller et al. 1989). Live specimens were captured and artificial cultures were established in Austin, Texas (1979) and Dexter, New Mexico (1980); however, these cultures were contaminated by Gambusia affinis, the western mosquitofish, in the early 1980s (Hubbs et al. 2008); the last G. georgei individual captured in the wild was taken in 1981, despite considerable efforts to secure this species since that time. Guillory (1980) noted a decline in G. georgei numbers and the possibility of extinction; in 1969, the population was estimated at less than 1,000, and surveys conducted in 1976 found no specimens.

     

    Habitat Associations

    Macrohabitat:

     

    Mesohabitat: Essentially restricted to shallow, quiet, mud-bottomed, shoreline areas without dense vegetation in thermally constant main channel; was common under shaded bridges (Guillory 1980).

     

    Biology

    Spawning season:

     

    Spawning habitat:

     

    Spawning behavior:

     

    Fecundity

     

    Age at maturation

     

    Migration:

     

    Growth and Population structure: 

     

    Longevity:

     

    Food habits:

     

    Phylogeny and morphologically similar fishes

    Gambusia georgei most distinct Gambusia morphologically and not closely related to any other species (Guillory 1980).

     

    Host Records

     

     

    Commercial or Environmental Importance

     

     

    References

    Guillory, V. 1980. Gambusia georgei (Hubbs and Peden), San Marcos gambusia. pp. 540 in D. S. Lee et al., Atlas of North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.

     

    Hubbs, C., and A.E. Peden. 1969. Gambusia georgei sp. nov. from San Marcos, Texas. Copeia (2):357-364.

     

    Hubbs, C., R.J. Edwards, and G.P. Garrett. 2008. An annotated checklist of the freshwater fishes of Texas, with keys to identification of species. Texas Journal of Science, Supplement, 2nd edition 43(4):1-87.

    Jelks, H.L., S.J. Walsh, N.M. Burkhead, S. Contreras-Balderas, E. Diaz-Pardo, D.A. Hendrickson, J. Lyons, N.E. Mandrak, F. McCormick, J.S. Nelson, S.P. Platania, B.A. Porter, C.B. Renaud, J.J. Schmitter-Soto, E.B. Taylor, and M.L. Warren, Jr. 2008. Conservation status of imperiled North American freshwater and diadromous fishes. Fisheries 33(8):372-407.

    Miller, R.R., J.D. Williams, and J.E. Williams. 1989. Extinctions of North American fishes during the past century. Fisheries 14(6):22-38.

     

    Page, L. M. & B. M. Burr.  1991.  A field guide to freshwater fishes of North America north of Mexico.  Houghton Mifflin Company, Boston, Massachusetts. 432 pp.

     

    Warren, M.L., Jr., B.M. Burr, S.J. Walsh, H.L. Bart, Jr., R.C. Cashner, D.A. Etnier, B.J. Freeman, B.R. Kuhajda, R.L. Mayden, H.W. Robison, S.T. Ross, and W.C. Starnes. 2000. Diversity, Distribution, and Conservation status of the native freshwater fishes of the southern United States. Fisheries 25(10):7-29.

     

    Records

    There are no records associated with this taxon yet.

    iSpecies Data

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    Occurences Over Time


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    Photos

    Credit: F. Douglas Martin Credit: F. Douglas Martin