The freshwater hatchetfish are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

, Gasteropelecidae, of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

from South and Central America. The

common hatchetfish The common hatchetfish or river hatchetfish (''Gasteropelecus sternicla'') is a tropical fish belonging to the freshwater hatchetfish family (Gasteropelecidae). Originating in South America in the Peruvian and middle Amazon Basin, Amazon, the Gu ...

is the most popular member among fish keeping hobbyists. The family includes three

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

: '' Carnegiella'' (four species), ''

Gasteropelecus ''Gasteropelecus'' is a genus of freshwater hatchetfishes found in Central and South America. This genus includes some popular aquarium fishes. There are currently three described species in this genus. Species * '' Gasteropelecus levis'' ( C ...

'' (three species), and '' Thoracocharax'' (two species).

Distribution and habitat

Freshwater hatchetfish originate from

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

(though they are absent from

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

). They tend to be an upper-level fish, often swimming directly below the surface of the water, biding their time patiently.

Size

When fully grown, freshwater hatchetfish typically range in size from . One exception is the giant hatchetfish (''

Thoracocharax securis ''Thoracocharax securis'', the giant hatchetfish, is a hatchetfish found in the Amazon River Basin. Adults will grow up to 6.8 cm in the wild and 9 cm in the aquarium. It is a rarely seen species in the aquarium hobby. It is known to gl ...

''), which can grow up to . The smallest species are the pygmy hatchetfish (''

Carnegiella myersi The pygmy hatchetfish (''Carnegiella myersi'') is a species of hatchetfish native to Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Br ...

''), which only grows to about , and the dwarf hatchetfish (''

Carnegiella schereri ''Carnegiella schereri'', a species of freshwater hatchetfish, is native to the Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area ...

''), which grows to about .

Flight

The most obvious trait of the freshwater hatchetfish is their enormously enlarged sternal region. This is accompanied by large

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s and "extraordinarily powerful" associated muscles which account for up to one-quarter of their total body weight. "Quick beats of the pectoral fins" allow hatchetfish to "lift themselves half out of the water and glide along the surface ... Some species can even leave the water for short stretches." Because of this ability to fly and tendency to jump, aquaria used to keep hatchetfish should have a tightly sealed cover to prevent these fish from escaping.

Genera

The genera in this family are: * '' Carnegiella''

Eigenmann Eigenmann () is a surname. Notable persons with that surname include: * Andi Eigenmann (born 1990), Filipino actress * Carl H. Eigenmann (1863–1927), German–American ichthyologist, husband of Rosa Eigenmann * Eduardo de Mesa Eigenmann, birth n ...

, 1909 * ''

Scopoli Giovanni Antonio Scopoli (sometimes Latinized as Johannes Antonius Scopolius) (3 June 1723 – 8 May 1788) was an Italian physician and naturalist. His biographer Otto Guglia named him the "first anational European" and the "Linnaeus of the Au ...

, 1777 * '' Thoracocharax'' Fowler, 1907

Distribution and habitat

Size

Flight

Genera

References

Further reading