Tropical Hatchetfish, Argyropelecus lychnus
The Tropical Hatchetfish, Argyropelecus lychnus, whose common Spanish name is pez hacha plateado, is a species in the Marine Hatchetfish or Sternoptychidae Family, known collectively as peces hacha in Mexico. Globally, there are seven species in the genus Argyropelecus, all of which are found in Mexican waters of the Atlantic and the Pacific.
The Tropical Hatchetfish have disc-shaped and laterally compressed bodies that taper toward the end. They are silvery in color with a black band dorsally. Their anal, caudal, and dorsal fins are transparent and their caudal fin base is long and narrow. Their head is short with a vertical mouth and large recessed eyes. There have two spines on their gill covers: the upper one is curved outward and the lower one points downward and is curved forward. They have a prominent row of photophores along their underside. Their anal fin has no spines and 12 rays. Their first dorsal fin has 9 rays. They are covered with scales.
The Tropical Hatchetfish are a mesopelagic species found at depths between 600 and 2,010 feet. They reach a maximum length of 5.6 cm (2.3 inches). They consume copepods and planktonic organisms. Reproduction is oviparous with planktonic eggs and larvae. They are believed to have a lifespan of less than one year. They are a poorly studied species and very little is known about their behavioral patterns.
The Tropical Hatchetfish are found in all Mexican waters of the Atlantic and the Pacific.
The Tropical Hatchetfish is most likely confused with the Pacific Hatchetfish, Argyropelecus affinis (extended oval body; long tail base).
The Tropical Hatchetfish are a small and very deep water species. They are abundant but seldom seen by humans. They are of limited interest to most. From a conservation perspective, they are currently considered of Least Concern, with a wide distribution and strong stable populations.
Tropical Hatchetfish, Argyropelecus lychnus. Fish collected in a deep water trawl net off Point Loma, California, August 2010. Length: 2.5 cm (1.0 inch). Collection and identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, CA.