The hatchetfishes (family Gasteropelecidae) include nine species of small, extremely compressed, deep-bodied fishes in three genera that are found, collectively, from Panama to the Río de la Plata in Argentina. Hatchetfishes have a highly developed pectoral fin musculature attached to the sternum; the chest muscles and sternum may account for as much as 25% of the animal’s weight. The resulting shape resembles a hatchet. The dorsal profile is nearly a straight line. (Berra 2007 and references therein)
Gasteropelecus maculatus, one of three known Gasteropelecus species, is found on the Pacific slopes of Panama and in the Pacific and Atlantic drainages of Colombia to the Maracaibo basin of Venezuela (Berra 2007 and references therein). The diet includes small crustaceans, larvae and mosquitoes (Galvis et al. 1997, cited in Froese and Pauly 2011). These are popular aquarium fishes, but their proclivity for jumping makes a well covered enclosure essential.