Family Sternoptychidae

Common names:  hatchetfishes

Distribution:  Worldwide primarily in the mesopelagic and occasionally in the bathypelagic zone.

General description and features:  This familiy of fishes are commonly known as the hatchetfishes because of their slender profile and sharply keeled scales on their belly.  They have rows of photophores in pockets along their bellies that cast light in a downward direction. These fishes are generally small reaching a size of about 8 cm.

Feeding:  These fishes generally consume small crustaceans such as copepods, amphipods, and euphausids.

Reproduction and life history:  Male hatchetfish possess large olfactory organs and it appears that they follow pheremone trails produced by the females for mating.  This is a strategy that would enhance the chances of finding a mate in a large sparsely populated environment.  Many small eggs are broadcast into the water column and the larvae develop at depths greater than 100 meters.  Spawning seasons appear to be rather lengthy or continuous throughout the year and are the population is not synchronized.  It has been suggested that some hatchetfish may only live for one year.

This is a photo of a dead hatchetfish Argyropelecus sp. from the eastern North Pacific (Photo by J. Drazen).  Notice the rows of light organs along the belly and sides.  If you look closely you will also notice that the eye is looking directly upwards.  This specimen is a bit damaged but the eye is actually tubular to enhance its ability to collect light from above.

This is a view of the belly of the same fish to show just how slender their profile is (Photo by J. Drazen).

Here is a photo of the dollar hatchetfish (Sternoptyx sp.) also from the eastern North Pacific (Photo by J. Drazen). This species typically lives at greater depths than Argyropelecus and lacks the upward directed tubular eyes.