The freshwater hatchetfish are a

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

, 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 h ...

from South and Central America. The common hatchetfish 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'' (four species), '' Gasteropelecus'' (three species), and '' Thoracocharax'' (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 Co ...

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 sou ...

(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 eas ...

). 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 which can grow up to 3 1/2 inches. The smallest being the two species, the Pygmy hatchetfish Carnegiella myersi which only grows to about 0.9 inch (2.2 centimeters), the Dwarf Hatchetfish Carnegiella schereri 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 se ...

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'' * '' Gasteropelecus'' * '' Thoracocharax''

Distribution and habitat

Size

Flight

Genera

References

Further reading