About the Lancetfish

Piercing the darkness of the twilight zone, the aptly-named lancetfish stops at nothing in pursuit of its target. Whether that’s a tasty polychaete worm, a plastic bottle, or a member of its own family, this voracious predator will ambush anything its large eyes detect and incapacitate it with its sharp, backwards-pointing fangs. If it’s already full, no matter: researchers once found over 70 hatchetfish in a specimen’s expandable stomach. Slow digestion means that the lancetfish can go for a while without a meal in the feast-or-famine middle ocean. The relatively intact state of the lancetfish’s lunch is also helpful to researchers investigating the twilight zone food web. It may even help scientists studying the fate of plastics in the deep ocean, since its seemingly bottomless pit of a stomach can act as a proxy for a scientific sampling net.

Measuring up to two meters (6.6 feet) in length, lancetfish are some of the biggest creatures in the twilight zone. That makes them a prized treat for larger fish like tuna, which can easily outswim this watery-muscled fish. Its skeleton and spiky fins are very delicate, but the lancetfish is not defenseless: silvery coloration and a slim profile disguises it from predators attacking from below.

With the exception of the polar seas, lancetfish are found throughout the world’s ocean at an impressive range of 100 to 2,000 meters—or 330 to over 6,000 feet—below the surface. Life in the vast twilight zone can get a little lonely, so lancetfish do what they can to find a date. If they encounter another lancetfish of the same gender, these simultaneous hermaphrodites simply change their sex. This doubles the odds of mating—but also the chance of getting more than a love bite. Lancetfish are infamous for eating members of their own family.

Related OTZ Story

Quick Facts

Common NameLancetfish
Scientific NameAlepisaurus ferox (long-snouted) and Alepisaurus brevirostris (short-snouted)
Other NamesLongnose lancetfish, cannibal fish
SizeUp to 2 meters (6.6 feet) and 9 kg (20 pounds)
DiscoveryR.T. Lowe, 1833 (long-snouted); Robert Henry Gibbs, 1960 (short-snouted)
Eats what?Crustaceans, amphipods, polychaete worms, squid, larvae, smaller fish like hatchetfish, fangtooths, and other lancetfish
Eats how?Ambushes prey, incapacitating it with two upper fangs. Opportunistic feeder digests on an as-needed basis.
Is eaten by?Yellowfin tuna, swordfish, opah, fur seal, Pacific cod, salmon shark