The Virtual Aquarium of Virginia Tech--Livebearers

Eastern Mosquitofish, Gambusia holbrooki

As their name implies, these fish have a unique form of reproduction, they bear live young. Males in this family have an elongated anal fin (gonopodium) to accomplish internal fertilization. About 150 species are found worldwide, most are fresh and saltwater tropical fish (swordtails and mollys), about 19 species are found in freshwaters in North America; one species, the eastern mosquitofish, is found in Atlantic drainage rivers in Virginia. Tolerant, mosquitofish have been widely distributed to control mosquito larvae in shallow stagnant-water swamps, marshes, ponds, and ditches throughout the United States. Livebearers such as the guppy, swordtails, and mollys are favored aquarium fishes because of they are small, hardy, colorful fishes with interesting reproductive habits.

 
Physical Description: 
ï¿½	Narrow, elongate body
ï¿½	Supraterminal, small mouth
ï¿½	Short head
ï¿½	Large eye
ï¿½	Teeth on jaws
ï¿½	Rounded tail fin
ï¿½	Anal fin located close to the abdomen 
ï¿½	Dorsal fin is located on the posterior part of the body
ï¿½	Dark, narrow bars horizontal or vertical on the body 
ï¿½	Black cheeks
ï¿½	Olive-colored body with green and purple glints

Similar species: 
ï¿½	Mosquitofish (Gambusia affinis)

Mean body size:
ï¿½	Adults are 20-40 mm standard length 

Habitat:
ï¿½	Shallows and marshes, and pools and backwaters of streams
ï¿½	Shores of ponds, lakes, and reservoirs

Distribution in VA:
ï¿½	Atlantic slope drainages and Delmarva peninsula

Food Habits:  
ï¿½	Aquatic and terrestrial insects, worms, microcrustaceans, mites, snails, and algae

Reproductive Habits: 
ï¿½	Mature rapidly, and may reproduce 4-6 weeks after birth
ï¿½	Spawning occurs mid-April to September in water 15.5-20ï¿½C
ï¿½	3-4 weeks for young to develop inside female, young are born live
ï¿½	1-354 young per brood

Population Status, Economic, or Ecological Importance: 
ï¿½	Hardy species
ï¿½	Good for mosquito control, but introductions of this fish have helped cause the decline of similar fish species that are native

References:       

Jenkins, R.E and N.M. Burkhead. 1993. Freshwater Fishes of Virginia. American Fisheries Society, Bethesda, Maryland.

If you are seeking more information for the above species click on the VAFWIS logo (The Virginia Fish and Wildlife Information Service):

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