Fish
Giant Oarfish
Regalecus glesne · also called oarfish, king of herrings, ribbonfish
The giant oarfish is the longest bony fish in the world and one of the strangest animals ever to wash up on a beach — a silver ribbon several metres long, edged with a scarlet fin, that lives in the deep open sea and is almost never seen alive. For centuries, the rare carcass or surface sighting was all people had to go on, and it fed stories of sea serpents.
Overview
Giant oarfish live in the open ocean across temperate and tropical waters worldwide, in the mesopelagic or “twilight” zone, roughly 200 metres to a kilometre down. They are not schooling fish; they appear to drift alone through the vast mid-water. Because they live where few nets reach and are too fragile to survive capture, virtually everything known about the living fish comes from a handful of submersible encounters and from strandings — dead or dying animals brought to the surface and shore by currents, storms, and illness.
A living ribbon
An oarfish’s body is a thin, deep, scaleless silver band that can be over 8 metres long but only a few centimetres thick, tapering to a point at the tail. A bright red dorsal fin runs the entire length, beginning in a crest of long spines above the head. There is no true tail fin and no swim bladder. The oarfish moves by sending waves along the dorsal fin while holding the body fairly still, and it often orients head-up, hanging vertically in the water — possibly to look for the silhouettes of prey against the light above.
Feeding
Despite its size, the oarfish is a gentle planktivore. It has no teeth; instead, fine gill rakers strain krill, other small crustaceans, and tiny fish and squid from the water. This diet of abundant, low-value food suits a large animal that moves slowly and expends little energy.
Myths: serpents and earthquakes
The oarfish’s shape, size, and rarity have made it a magnet for folklore. It is the leading real-world candidate for the sea serpent of sailors’ tales. In Japan it is the ryugu no tsukai, a messenger from the undersea dragon king’s palace, and a widespread belief holds that oarfish strandings foretell earthquakes. Scientific analyses have found no correlation between deep-sea fish appearances and seismic events; strandings track oceanographic conditions and the fish’s own frailty instead.
Status
The giant oarfish is listed as Least Concern, though its true population is unknown. It is not targeted by fisheries, rarely taken as bycatch, and lives in a habitat little disturbed by people, so there is no evidence of decline. Its scientific value lies in what it reveals about life in the open mid-ocean — and in finally replacing myth with observation as submersibles and cameras reach its world.
Giant Oarfish: common questions
Is the oarfish the origin of sea serpent legends?
Almost certainly, in part. A silvery, ribbon-shaped fish several metres long, sometimes with a crest of red fin spines on its head, undulating at or near the surface, matches historical descriptions of sea serpents closely. Dead or dying oarfish washing ashore, or being seen writhing at the surface, would have been startling and inexplicable to earlier sailors, and the "king of herrings" and "ribbonfish" names reflect long familiarity with the occasional carcass.
Do oarfish predict earthquakes?
There is no scientific evidence that they do. The idea is strongest in Japan, where oarfish are traditionally seen as omens, and it gained attention after several washed up before the 2011 Tōhoku earthquake. But studies comparing oarfish and other deep-sea fish strandings with subsequent seismic activity have found no meaningful link — the appearances are better explained by ocean currents, storms, upwelling, and the fact that a sick oarfish simply cannot stay at depth.
How does such a long, fragile fish live?
Slowly and gently. The oarfish drifts in the open mid-water, holding itself vertically or horizontally and propelling itself with a rippling motion of the long red dorsal fin while keeping the ribbon-like body relatively rigid — an efficient, low-energy way to move. It has no teeth; it feeds by straining krill and other small animals through gill rakers. It has no swim bladder and its body is mostly water and gelatinous tissue, so it is nearly weightless in the sea but falls apart quickly out of it.
Why are oarfish so rarely seen alive?
They live in the sparsely populated open ocean at depths of a few hundred metres to a kilometre, they are not caught in normal fisheries, and they are physically too delicate to survive being netted. Almost every oarfish humans have examined was either dead on a beach, floating sick at the surface, or filmed briefly by a deep submersible. Live footage in the wild was not obtained until the 2000s.