Florida Museum of Natural History
hdr_home (36K)
  HOME COLLECTION EDUCATION IMAGE GALLERY SOUTH FLORIDA ORGANIZATIONS MEETINGS STAFF
  SHARK FRESHWATER
RESEARCH
BIOLOGICAL
PROFILES
JUST FOR KIDS SITE LINKS FLMNH

Education

Biological Profiles




PIKE KILLIFISH
Order - Cyprinodontiformes
Family - Poeciliidae
Genus - Belonesox
Species - belizanus
Belonesox belizanus

Taxonomy

Rudolf Kner, an Austrian ichthyologist whose background included formal training as a physician, described the pike killifish in 1860, erecting a new genus, Belonesox, in recognition of this distinctive fish. Carl L. Hubbs recognized two subspecies of pike killifish in 1936, Belonesox belizanus belizanus and the more robust Belonesox belizanus maxillosus


Common Names

Pike killifish (English), pike livebearer (English), pike topminnow (English), topminnow (English), gelber hechtkärpfling (German), hechtkärpfling (German), lebendgebärender hechtkärpfling (German), pepesca gaspar (Spanish), szczupaczek zyworodny (Polish), and zhivorodyaschaya schuchka (Russian).


Geographical Distribution

The native range of the pike killifish extends from the Atlantic slope drainages of Veracruz, Mexico, east through the Yucatan, Belize, Guatemala, Honduras, Nicaragua, and northern Costa Rica. A non-native population of B. belizanus maxillosus in Southern Florida, USA was established in 1957 and persists today.



World distribution map for the pike killifish
Map


Habitat

Pike killifish prefer the warm surface waters of slow flowing rivers, ponds, and lakes, particularly those with abundant aquatic vegetation. A common resident of near shore and backwater habitats, the pike killifish is tolerant of low levels of dissolved oxygen. This physiologically labile fish may also be found in brackish water habitats such as lagoons and estuaries as well as marine environments with salinity levels as high as 40ppt.

Taylor Slough, Florida -
habitat of the non-native pike killifish

© South Florida Water Management District
Taylor Slough

Biology
· Distinctive Features
The long, toothy jaws of the pike killifish, which lend this fish something of a menacing appearance, distinguish this livebearer from all others. In keeping with other livebearers, males possess a readily observable gonopodium, a modified anal ray that serves to facilitate internal fertilization. The pike killifish is not likely to be confused with any other cyprinodontiforms or "killifishes" (a term broadly applied to certain species of both live-bearing and egg-laying Cyprinodontiform fishes).


· Coloration
The overall body color of the pike killifish is light beige, darkening dorsally. Many rows of numerous, small black spots are present on the lateral upper half of the fish, with those spots just anterior to the midbody largest and darkest. A large black spot is present at center or slightly above center of the caudal peduncle. Cryptic young possess a dark lateral stripe that presumably aids in their ability to mimic small twigs or plant litter as they float motionless at the surface.


· Size, Age & Growth
Obtaining a maximum total length of 150mm, the pike killifish is the largest member of the family Poeciliidae. As a rule, females are larger than males, and growth being rapid, reproductive maturity is typically achieved within 6-12 months. On average, pike killifish are approximately 15 or 16mm at birth. Like most livebearers, pike killifish are likely short-lived.


· Food Habits
The pike killifish is a piscivore that in its native habitat feeds largely on other surface or near surface dwelling poeciliids such as the familiar mosquitofishes, swordtails, and platies. Juveniles prey on other juvenile or larval fishes. Pike killifishes of all sizes are reported to engage in cannibalism.


The platyfish (Xiphophorus variatus) is a prey item
of the pike killifish in its native habitat

© George Burgess
Platyfish


· Reproduction
Poeciliids are ovoviviparous; fertilization is achieved internally. Males inseminate females through the use of the gonopodium. The fertilized ova develop within the female, the end result of which is the birth of live young. Given favorable conditions, livebearers living in tropical environments often breed year round and pike killifish are no exception. One laboratory study determined that female pike killifish store sperm and depending on environmental factors produce on average one brood every 38 to 49 days. However, the highest reproductive outputs among these fish tend to coincide with the rising waters brought on by the rainy season.

Pike killifish broods can be quite large with as many as 322 young recorded in a single brood, qualifying the pike killifish for the ranking of second most fecund poeciliid.


· Predators
Juveniles and adults alike fall prey to a wide variety of aquatic predators including other predatory fishes, piscivorous reptiles and aquatic invertebrates. As surface dwellers, these fishes are likely very susceptible to predation by wading birds.


Predators of the pike killifish -
great blue heron and snowy egret

© South Florida Water Management District
Great Blue Heron


Importance to Humans

At one time, pike killifish were of importance to medical science as research animals. It is interesting to note that the introduced population in south Florida stems from the release of pike killifish that were the subject of a medical research program whose funding had been terminated. Pike killifish are also of some value to aquarists, but due to their aggressive piscivory and cannibalistic tendencies their potential for wide spread popularity has been limited.

Conservation

This species is not listed as threatened or vulnerable by the World Conservation Union (IUCN). The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.



Prepared by:

Robert H. Robins