AskDefine | Define Killifish

Dictionary Definition

killifish n : small mostly marine warm-water carp-like schooling fishes; used as bait or aquarium fishes or in mosquito control [also: killifishes (pl)]

Extensive Definition

A killifish is any of various tiny , oviparous (egg-laying) cyprinodontiform fish (including families Aplocheilidae, Cyprinodontidae, Fundulidae, Profundulidae, Rivulidae and Valenciidae). All in all there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species. Although killifish is sometimes used as an English equivalent to Cyprinodontidae, some species belonging to that family have their own common names, such as the pupfish and the mummichog. The name killifish is derived from the Dutch word "kilde", meaning small creek, puddle. Most killies are small fish, one to two inches (2.5 to 5 cm). The largest is under six inches (15 cm), but only a few species are this large.Striped killifish tend to live from a range of 10 months to a year and a half. Killifish provide food for wading birds, aerial birds and some ducks. Fishers also use them as bait while fishing and other recreational fishing games.

Range and habitat

Killifish are found mainly in fresh or brackish waters in the Americas, as far south as Argentina and as far north as southern Ontario. There are also species in southern Europe, in much of Africa as far south as KwaZulu-Natal, South Africa, in the Middle East and Asia (as far east as Vietnam), and on several Indian Ocean islands. Killifish are not found in Australia, Antarctica, or northern Europe.
The majority of killifish are found in permanent streams, rivers, and lakes, and live between two and three years. Such killifish are common in the Americas (Cyprinodon, Fundulus and Rivulus) as well as in Africa and Asia (including Aphyosemion, Aplocheilus, Epiplatys, Fundulopanchax and Lacustricola) and southern Europe (Aphanius). Some of these habitats can be rather extreme; the only natural habitat of the Devil's Hole pupfish (Cyprinodon diabolis) is Devil's Hole: a cavern at least 300 feet deep, branching out from a small opening at the surface, approximately 6 feet by 18 feet wide.
Some specialized forms live in temporary ponds and flood plains, and typically have a much shorter lifespan. Such species, known as "annuals", live no longer than nine months, and are used as models for studies on aging. Examples include the African genus Nothobranchius and South American genera ranging from the cold water Austrolebias of Argentina and Uruguay to the more tropical Gnatholebias, Pterolebias, Simpsonichthys and Terranatos.

Territorial behavior

A small number of species will shoal while most are territorial to varying degrees. Populations can be dense and territories can shift quickly, especially for species of the extreme shallows (a few centimetres of water). Many species exist as passive tribes in small streams where dominant males will defend a territory while allowing females and immature males to pass through the area. In the aquarium, territorial behavior is different for every grouping, and will even vary by individuals. In a large enough aquarium, most species can live in groups as long as there are more than three males.


Killifish feed primarily on aquatic arthropods such as insect (mosquito) larvae, aquatic crustaceans and worms. It is reported by the killifish collector Rudolf Koubek that areas in Gabon where the streams lack killifish (due to pollution or other causes) are rife with malaria, which is spread by a mosquito. Some species of Orestias from Lake Titicaca are planktonic filter feeders. Others, such as Cynolebias and Megalebias species and Nothobranchius ocellatus are predatory and feed mainly on other fish.

Killifish as pets

Many killifish are lavishly coloured; and most species are easy to keep and breed in an aquarium. Specimens can be obtained from specialist societies and associations. Striped panchax are commonly found in pet shops, but caution must be exercised when considering tank mates, since the mouth of the Striped panchax is as wide as the head, and much smaller fish will be eaten.

External links


  • Costa, Wilson J.E.M. (1998). Phylogeny and Classification of the Cyprinodontiformes (Euteleostei: Atherinomorpha): A Reappraisal. In Malabarba, L. et al. (eds), Phylogeny and Classification of Neotropical fishes part 6 (Atherinomorpha), Porto Alegre. 603 p.
  • Huber, J. (2004). Killi-Data Online
  • Parenti, Lynn R. (1981). A phylogenetic and biogeographical analysis of Cyprinodontiform fishes (Telostei, Alethrinimorpha). Bulletin of the American Museum of Natural History 168, article 4.
  • Fish Lives in Logs, Breathing Air, for Months at a Time- Aalok Mehta, National Geographic News.
Killifish in German: Aplocheilidae
Killifish in Italian: Killifish
Killifish in Japanese: 卵生メダカ
Killifish in Dutch: Killivissen
Killifish in Polish: Szczupieńczykowate
Killifish in Portuguese: Aplocheilidae
Killifish in Russian: Карпозубые
Killifish in Swedish: Äggläggande tandkarpar
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