The freshwater hatchetfishes are a family, Gasteropelecidae, of ray-finned fish. The common hatchetfish is the most popular member among fish keeping hobbyists. The family includes three genera: Carnegiella (4 species), Gasteropelecus (3 species), and Thoracocharax (2 species).

Distribution and habitat

Freshwater hatchetfishes originate from Panama and South America (though they are absent from Chile). They tend to be an upper-level fish, often swimming directly below the surface of the water.

Flight

The most obvious trait of the freshwater hatchetfish is their enormously enlarged sternal region. This is accompanied by large pectoral fins and "extraordinarily powerful" associated muscles which "account for up to 1/4 the 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"^[1] Because of this ability to fly and tendency to jump, aquariums used to house hatchetfish should have a cover which is tightly sealed to prevent these fish from escaping.

Genera

There are three genera in this family:

• Genus Carnegiella
• Genus Gasteropelecus
• Genus Thoracocharax

References

Additional reading

• "Gasteropelecidae". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=163118. 
• Froese, Rainer, and Daniel Pauly, eds. (2011). "Gasteropelecidae" in FishBase. October 2011 version.
• Nelson, Joseph S. (2006). Fishes of the World. John Wiley & Sons, Inc. ISBN 0-471-25031-7

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