The Largehead Hairtail (Trichiurus lepturus) is a large, slender fish found in both Endless Ocean and Endless Ocean: Blue World.

It has shiny silver scales and a long dorsal fin that runs the entire length of its back. It swims in an odd manner to hunt, with its head up and its tail down.

Encyclopedia Description

Endless Ocean

"These fish have long, skinny bodies that narrow to a thread-like spine. While their dorsal fins stretch the entire length of their backs, they have no ventral or tail fins. They are a bold silvery white color and can be seen year-round near Deep Valley.

They are usually found schooling in deep water near the ocean floor but come closer to the surface when searching for food. While hunting, they swim in an upright position and wait for prey to swim overhead before ambushing them. When not looking for food, they swim horizontally, with juveniles tending to lower their heads.

Their bodies are covered in an unusual kind of scale that contains a silvery substance known as guanine. Guanine is used in the manufacture of fake pearls, nail polish, and some shampoos and paints."

Endless Ocean: Blue World

"Its long, sleek, silver body resembles a sword. It has no scales and is covered in a silvery substance called guanine. Guanine is used in nail polish and imitation pearls."

[Strange Way of Swimming]

"The largehead hairtail lives in schools on the deep ocean floor. It swims with its head raised and body angled vertically, waiting for prey to pass overhead.

At full speed it swims with its body at a horizontal angle, and young fish swim with their heads lowered and bodies angled downwards."


Endless Ocean


  • In Secret Lake, during its Tanga Day event that lasts from the 17th to the 23rd of November.


  • Near Deep Valley, a sizeable shoal can be found to the southeast of coordinates E-6 swimming almost stationary at mid-depth, near the octopus which is also found in the area.

Endless Ocean: Blue World

During the daytime, a shoal of largehead hairtails is located in the room to the east of the Mermaid's Ballroom, across coordinates D-2 and D-3 in Valka Castle. At night, a school can be seen floating around the Well of the Full Moon in Ciceros Strait's Triton Village Ruins.


These fish float around slowly, in large, loose groups. Sometimes, they exhibit the behavior noted in both of their in-game descriptions, and swim with their head pointed upwards. The player can unlock their trivia information in Blue World by feeding them.


  • In Endless Ocean, these fish are always found swimming with their bodies laid horizontally, unlike in Endless Ocean: Blue World, where they can be found swimming facing upwards, with their bodies laid vertically.

Real-Life Information

  • The largehead hairtail is seen and described as swimming in-game with its head up and its tail down. This is an accurate reflection of its real-life hunting practices, wherein it faces upwards in the water in order to make itself less obvious as a threat, and lunges at anything that swims overhead[1]. Information on the other swimming habits is hard to come by.
    • These fish share their unusual manner of swimming with polka-dot ribbonfish (though only young ribbonfish swim strangely, and for different reasons)[2]. Other fish with similar behaviors are the oarfish, which often swims vertically in real life but does not display this behavior in-game, and the razorfish, which swims vertically in order to disguise itself amongst the spines of sea urchins (another behavior not shown in-game)[3][4].
  • Another accurately-reported behavior is a preference for schooling near the ocean floor, though said report is incomplete. In real life, Young fish and small adults reside in deeper waters during the day, and full-grown fish may rise to the surface in order to pursue prey. At night, the young and small group rises to the surface while the large adults take to the bottom[5][6]. However, they do show a preference for deeper water overall, usually between 330 and 1100 feet (100 and 350 meters)[7][8].
  • As noted in the in-game description from the first game, the largehead hairtail has no ventral fins (also called pelvic fins) and no tail fin (also called a caudal fin)[9][10].
  • The substance guanine is accurately described in the largehead hairtail's in-game descriptions, as it is indeed used in cosmetics and other places to impart a pearly sheen to the product in question[11]. However, guanine is perhaps more well-known as one of the four constituents of DNA; the other three are adenine, ctyosine, and thymine[12].
    • The reflective silver color granted by guanine is described as "steely blue with silver reflections" in life, but becomes "uniformly silver-grey" after the fish dies[13].
  • These fish have barbed, sharp, and very long teeth, something that is not noted in their in-game model or description[5]. They pose no threat to the player, though they have been noted to bite people in real life from time to time[14].
  • These fish are a common market fish in Eastern Asia. They are eaten either grilled or fried, as well as sometimes being eaten raw as sashimi[6]. They are not as often sold for food in the United States, and are actually considered pesky, as they steal bait from anglers that are seeking out other fish[14].
    • Despite their status as a sought-out food source in some parts of the world, they re not considered endangered[8].
  • Other common names for the largehead hairtail include cutlassfish, Atlantic cutlassfish, Cox's hairtail, Australian hairtail, and largehead ribbonfish[5][6][7][15].



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