details

Description

Male is pictured above and female is pictured below.

This smaller fish (1.8-3.5 in.) is silver in color with yellow tints on the underside of the fish and olive green above. It has one dorsal and one anal fin with no lateral line; the pectoral fins are large in relation to the rest of the body. During the breeding season, males become very colorful with steel blue, bright green and salmon-pink colors.

Ecological Threat

As opposed to competition for food or habitat, this species poses a reproductive threat to native Cyprinodon species. While it does provide some competition for habitat, it primarily threatens them through hybridization (crossing of two species). The sheepshead minnow is able to breed with native species of the Cyprinodon genus, which can cause the two species to merge into one species, favoring the sheepshead minnow and eliminating already endangered native Cyprinodon species. Hybridization events can lower the biodiversity in a habitat and affect food web structure.

Biology

They are a hardy species that can survive in very shallow and oxygen-deprived salt or freshwaters. After three months, the sheepshead minnow reaches sexual maturity, and spawning events can happen from February through October. Females can spawn numerous times during the season and can release up to 300 eggs per spawning period. After 4-12 days, the eggs hatch into larvae.

History

It was first reported from Lake Balmorhea in the 1960s, with blame focusing on bait-bucket releases. It appeared in Leon Creek by the 1970s and the Pecos River proper by the early 1980s.

Native Origin

Atlantic Coast and Gulf of Mexico, and down along the South America coastline.

TX: Native to Brazos River drainage system and estuarine waters along the Gulf of Mexico.

Current Location

U.S. Habitat: They can tolerate freshwater and saltwater, and prefer shallow waters. They can be found in creeks, canals, saltwater bays and estuaries.

U.S. Present: Invasive to the Pecos River, Lake Balmorhea and Leon Creek.

For a point collection map provided by the U.S. Geological Survey click here.

Resembles

Comanche springs pupfish (Cyprinodon elegans), Pecos pupfish (C. pecosensis) and Leon Springs pupfish (C. bovinus).

Management

With hybridization being their main threat, the full removal of the species from its invasive habitat would be the only way to protect native species. However, once invasive species are established, the complete removal of them is nearly impossible. The best prevention is to not dump live bait while fishing.

References

Echelle, A.A. and Echelle, A.F., 1997. Genetic Introgression of Endemic Taxa by Non‐natives: A Case Study with Leon Springs Pupfish and Sheepshead Minnow: Introgresión Genética de Taxas Endémicos Debido a Especies No‐nativas: Un Caso de Estudio del Pez Cachorro de Leon Springs y el Pez Bolín. Conservation Biology, 11(1), pp.153-161

Kennedy, S.E.1977. Life history of the Leon Springs pupfish, Cyprinodon bovinus. Copeia 1977(1):93-1

Stevenson, M.M. and T.M. Buchanan. 1973. An analysis of hybridization between the cyprinodont fishes Cyprinodon variegatus and Cyprinodon elegans. Copeia 1973(4):682-692.

Wilde, G.R., and A.A. Echelle. 1997. Morphological variation in intergrade pupfish populations from the Pecos River, Texas, USA. Journal of Fish Biology 50(3):523-539.

Internet Sources

https://tpwd.texas.gov/huntwild/wild/species/sheepsheadminnow/

https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=662

http://txmarspecies.tamug.edu/fishdetails.cfm?scinameID=Cyprinodon%20variegatus