Common name: Least Killifish
Synonyms and Other Names: dwarf livebearer
available through www.itis.gov
Identification: Menhinick (1991); Page and Burr (1991); Mettee et al. (1996).
Size: females to 3.0 cm SL
Native Range: Lower Coastal Plain from South Carolina to southern Louisiana (Rosen 1979; Page and Burr 1991).
Puerto Rico &
Hydrologic Unit Codes (HUCs) Explained
Native range data for this species provided in part by NatureServe
Interactive maps: Point Distribution Maps
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Heterandria formosa are found here.
Table last updated 10/4/2018
† Populations may not be currently present.
Ecology: Heterandria formosa is one of the smallest freshwater fish species in North America, with females maturing at 15 mm SL (Bennett and Conway 2010). Inhabits still waters of pools and slow-moving streams in areas of dense vegetation (Boschung and Mayden 2004). Dwarf killifish are omnivorous, generally consuming aquatic invertebrates (ostracods, copepods, and cladocerans) but will also consume plant materal as well (Boschung and Mayden 2004).
Means of Introduction: In 1905 about 10,000 Heterandria and Gambusia were stocked into New Jersey for mosquito control purposes (Seal 1910). The reason for the North Carolina stocking is not known.
Status: The New Jersey population apparently did not survive; the species is established in North Carolina.
Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.
References: (click for full references)
Bennett, M.G., and K.W. Conway. 2010. An overviwe of North America's diminutive freshwater fish fauna. Ichthyological Exploration of Freshwaters. 21(1):63-72.
Boschung, H.T., Jr. and R.L. Mayden. 2004. Fishes of Alabama. Smithsonian Books, Washington, D.C.
Krumholz, L. A. 1948. Reproduction in the western mosquito fish, Gambusia affinis affinis (Baird and Girard), and its use in mosquito control. Ecological Monographs 18:1-43.
Menhinick, E. F. 1991. The freshwater fishes of North Carolina. North Carolina Wildlife Resources Commission. 227 pp.
Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.
Seal, W. P. 1910. Fishes in their relation to the mosquito problem. Bulletin of the U.S. Bureau of Fisheries 28(1908):831-838.
Leo Nico, Pam Fuller, and Matt Neilson
Revision Date: 6/27/2011
Peer Review Date: 4/1/2016
Leo Nico, Pam Fuller, and Matt Neilson, 2019, Heterandria formosa Girard, 1859: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=852, Revision Date: 6/27/2011, Peer Review Date: 4/1/2016, Access Date: 4/19/2019
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.