The Hatchetfish Family – Sternoptychidae
Three typical representatives of the Hatchetfish or Sternoptychidae Family are currently included in this website:
The Hatchetfish or Sternoptychidae Family, known as Marine or Deep-sea Hatchetfish and as peces hacha in Mexico, are small abundant silvery bioluminescent fish that are found in deep oceanic midwaters. They receive their common name from their body shape which resembles a “hatchet” with the tail base representing the handle. There are seventy-three global family members that have been placed in ten genera and are found in the Atlantic, Indian, and Pacific Oceans. There are seven global members in the genus Argyropelecus and four global members in the genus Sternoptyx; which are collectively known as Silver Hatchetfish.
The Hatchetfish have extremely compressed disc-shaped bodies with a deep keel, large eyes with keen eyesight, a large oblique mouth with small teeth, pectoral and pelvic fins found well back on the body, and a series of photophores along the lower sides of their head and body. Most have a small adipose fin. They are small in stature ranging from 2.8 cm (1.1 inches) to 12 cm (4.7 inches) in length. Their anal fins have 11 to 38 rays that may be divided into two parts. Their bodies are covered with silvery scales.
Most Hatchetfish reside in very deep offshore waters at depths between 600 and 1,800 feet and undergo daily vertical migrations moving to shallower waters at night to feed and returning to the ocean depths for protection during the day. They prey on amphipods, copepods, euphausiids, ostracods, and fish that are smaller than themselves. They live sluggish non-mobile lifestyles. They are well-camouflaged due to their silvery color and are able to avoid predation using their series of downward-pointing photophores and their darkly-pigmented dorsal surface. This bioluminescent counter-illumination involves the production of varying amounts of light by each fish to camouflage its silhouette from predators found below. Many species have transparent anal, caudal, and dorsal fins. Reproduction is oviparous with external fertilization that occurs in open water. Offspring are not guarded. Most are short-lived with a lifespan of less than one year. They are very small, poorly studied and of limited interest to most, thus very little is known about their behavioral patterns.
From a conservation perspective, the Hatchetfish are currently considered of Least Concern, with stable populations over wide geographic ranges, however, these populations are poorly monitored.