The freshwater hatchetfish are a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

, Gasteropelecidae, of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

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, the Guianas and Venez ...

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

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

: ''

Carnegiella ''Carnegiella'' is a genus of freshwater hatchetfishes found in the Amazon and Orinoco basins in South America. This genus contains some popular aquarium fishes. Species There are currently four recognized species in this genus: * '' Carnegiel ...

'' (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 ''Thoracocharax'' is a genus of freshwater hatchetfishes found in the Amazon Basin, Amazon, Orinoco and Paraná River, Paraná basins in South America. These fish live just under the surface of the water. Species FishBase recognizes two species ...

'' (two species).

Distribution and habitat

Freshwater hatchetfish originate from

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

(though they are absent from

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

). 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 range in size from 1 inch up to 2 1/2 inches. 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 g ...

which can grow up to 3 1/2 inches. The smallest being the two species, the Pygmy hatchetfish

Carnegiella myersi The pygmy hatchetfish (''Carnegiella myersi'') is a species of hatchetfish native to Peru. Named for ichthyologist George S. Myers George Sprague Myers (February 2, 1905 – November 4, 1985) was an American ichthyologist who spent most of hi ...

which only grows to about 0.9 inch (2.2 centimeters), 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 tributaries. The Amazon drainage basin covers an area of about ...

which only grows to about 1 inch (2.6 centimeters).

Flight

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

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

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: * ''

'' * ''

Distribution and habitat

Size

Flight

Genera

References

Further reading