How Rare Are Oarfish? The Truth About Sightings

Oarfish are among the rarest fish encounters on the planet, not because the species is necessarily on the brink of extinction, but because they live at depths most humans and most fishing gear never reach. Found primarily between 200 and 1,000 meters below the surface, these ribbon-shaped giants spend their lives in a part of the ocean we barely monitor. When one washes ashore or drifts into shallow water, it makes international news, which says more about how seldom it happens than about the fish itself.

Why Oarfish Are So Hard to Find

The main reason oarfish sightings are so unusual has nothing to do with population collapse or hiding behavior. It comes down to address: they live in the mesopelagic zone, a layer of ocean that sits below the sunlit surface waters where most fishing and diving take place. Research from Korea describes oarfish as “rarely found alive because they live in deep water (200–1000 m) and are few in number.”¹ That combination of deep habitat and naturally low abundance means the odds of a diver, fisherman, or beachgoer crossing paths with a living oarfish are vanishingly small.

The mesopelagic zone is also notoriously difficult to study. Trawl nets designed for commercial species rarely operate at the depths oarfish prefer, and even research trawls in that range cover tiny fractions of ocean volume. Most of what we know about living oarfish in their natural habitat comes from remotely operated vehicles (ROVs) operated by oil companies and research institutions. A study documenting five ROV sightings in the northern Gulf of Mexico between 2008 and 2011 recorded apparently healthy oarfish at depths ranging from the upper water column down to 463–492 meters, which at the time represented the deepest verified record for the species.² Five sightings across four years of intensive deep-sea camera work gives you a sense of just how sparse these animals are, even in waters where they are present.

How Often Do Sightings Actually Happen

There is no global database tracking every oarfish encounter, so putting a firm number on annual sightings is impossible. What exists instead is a patchwork of individual reports in scientific journals, museum records, local newspaper archives, and increasingly, social media posts. Each new stranding or shallow-water encounter tends to generate a flurry of coverage, which can create the impression that oarfish are suddenly appearing more often. In reality, the raw number of documented encounters across any given region remains low, often just a handful per decade.

In the Mediterranean, for instance, a 2024 review highlighted two specimens found in the northwestern Ionian Sea in consecutive years, 2021 and 2022, at depths of 525 and 350 meters respectively.³ Two specimens in two years across an entire sea basin would barely register for a common species. For oarfish, it was noteworthy enough to warrant a peer-reviewed paper updating the known distribution. That is the scale of rarity we are talking about.

The Gulf of Mexico ROV observations tell a similar story. Despite thousands of hours of deep-sea footage recorded as part of the SERPENT Project, researchers documented just five oarfish encounters over a multi-year period.² And those were the cameras running around the clock in exactly the depth range where oarfish are expected. If ROVs with floodlights in the right water column can go months without seeing one, recreational divers are working against far longer odds.

When Oarfish Come to the Surface

Nearly every oarfish sighting that makes the news involves an animal at or near the surface, often dead or dying. Healthy oarfish have little reason to leave the deep water where they feed and apparently spend their entire adult lives. The ones that wash up on beaches or drift into harbors are generally in distress, whether from disease, injury, disorientation, or water temperature changes. This introduces a sampling bias that colors public perception: people see oarfish only under abnormal circumstances, which makes the animals seem even more mysterious than they already are.

Occasionally, though, live young oarfish turn up in surprisingly shallow water. A study from Taiwan documented a young Russell’s oarfish captured alive by a stow net at just 15–18 meters deep near the Tamsui River mouth, alongside larval fish and crustaceans.⁴ Young oarfish may use shallower coastal waters during early life stages before moving to deeper habitat as they grow. This would explain some of the occasional sightings of smaller individuals near shore, even though adult oarfish are almost never found at those depths voluntarily.

Are Sightings Really Increasing

A common claim in news coverage is that oarfish sightings are “on the rise,” sometimes with ominous undertones about what it might mean. The reality is more mundane. More people now carry high-quality cameras everywhere. Fishing boats and research vessels increasingly run underwater cameras. Social media means a single photo from a remote beach in the Philippines reaches millions of viewers within hours, whereas decades ago the same stranding might have been recorded only in a local newspaper, if at all.

Japanese researchers who assembled a database of deep-sea fish appearances, drawing from newspapers, academic articles, and marine museum records, noted that newspapers have historically reported rare deep-sea fish sightings precisely because their unusual nature attracts readers.⁵ The same dynamic now plays out at global scale through social media. Each sighting gets amplified far beyond its actual significance. This creates a feedback loop where increased attention looks like increased frequency, when the underlying rate may not have changed at all.

That said, there is no rigorous monitoring program that could confirm or deny a genuine change in oarfish encounter rates. Without systematic population surveys, the question of whether oarfish are truly showing up more often, or whether we are just noticing them more, remains genuinely unanswered.

The Earthquake Myth

In Japan, a deeply rooted piece of folklore holds that oarfish appearances predict earthquakes. The fish is sometimes called “ryugu no tsukai,” roughly translated as “messenger from the sea god’s palace,” and a stranding is traditionally interpreted as a warning of seismic activity. This belief has crossed over into international media, and almost every time an oarfish washes ashore in Japan, headlines ask whether a major earthquake is imminent.

Researchers tested this directly. A study published in the Bulletin of the Seismological Society of America assembled a database of deep-sea fish appearances in Japan, focusing on species like oarfish and slender ribbonfish that are traditionally linked to earthquakes. The conclusion was unambiguous: “the spatiotemporal relationship between deep‐sea fish appearances and earthquakes was hardly found,” and the researchers characterized the folklore as “a superstition attributed to the illusory correlation between the two events.”⁵

The reasoning behind the myth has a certain plausibility on the surface. If oarfish live in deep water near the seafloor, and if pre-earthquake geological shifts disturb the deep-sea environment, then displaced oarfish might theoretically flee to the surface. The problem is that oarfish are mid-water swimmers, not bottom-dwellers. They feed in the water column rather than on or near the substrate. And as the Japanese study showed, when you compare the actual dates and locations of oarfish sightings against the record of seismic events, the overlap is no better than chance. Humans are excellent at noticing coincidences and poor at tracking base rates, which is exactly the kind of cognitive pattern that sustains this type of folklore.

What Oarfish Actually Look Like Up Close

Part of what makes oarfish sightings so dramatic is the animal’s appearance. These are the longest bony fish in the ocean, with confirmed specimens reaching over 8 meters and unverified reports stretching well beyond that. Their body is deeply compressed from side to side and tapers from a relatively thick front end to a threadlike tail. A detailed morphological review describes them as having small heads relative to their length, small round eyes, toothless jaws, and an extremely long dorsal fin that runs the full length of the body, with the first rays extending above the head like a scarlet crest.⁶

Their skin is almost entirely scaleless, covered instead with irregularly arranged tubercles that are most developed along the belly. They have a single elongated pelvic fin spine on each side, which in life trails behind the fish like a streamer, and no anal fin at all. The overall impression is something between a living ribbon and the kind of creature you would expect to find in a medieval bestiary. It is not hard to see how oarfish gave rise to sea serpent legends: a 5-meter oarfish undulating at the surface with its crimson dorsal crest erect would look alien to anyone unfamiliar with the species.

Self-Amputation and Other Oddities

Oarfish have a behavior that even experienced marine biologists find strange. They exhibit autotomy, which is the ability to deliberately shed the rear portion of their body. The same Korean taxonomic study notes that “oarfish exhibit autotomy or self-amputation of the posterior part of the body,” though researchers still do not know exactly why they do it.¹ The severed tail apparently does not regenerate. Many specimens found washed ashore or caught in nets are missing their posterior ends, which initially led some researchers to think they had been attacked by predators. It now appears that at least some of those truncated individuals had dropped their own tails.

One hypothesis is that autotomy serves as a predator escape mechanism, similar to how some lizards shed their tails. Another possibility is that it relates to reproduction or to shedding parasitic loads. The Gulf of Mexico ROV study documented the first record of an arthropod ectoparasite, an isopod, on a living oarfish, so parasitism is clearly something these animals deal with in the wild.² Without more observations of living oarfish in their habitat, the purpose of autotomy remains one of the genuine open questions in oarfish biology.

What We Know About Oarfish Reproduction

Almost nothing was known about oarfish reproduction until recently, for the simple reason that no one had ever witnessed spawning or successfully kept eggs in a laboratory. That changed in 2020, when Japanese researchers performed artificial insemination on a freshly stranded female oarfish and followed the fertilized eggs through to hatching. The eggs took 18 days to develop at water temperatures between 20.5 and 22.5 degrees Celsius. The larvae that emerged had features typical of their broader fish order, faced downward in the water, and swam using their pectoral fins. They frequently opened their mouths in what appeared to be feeding attempts.⁷

The larvae did not survive. Despite their apparent swimming ability and mouth-opening behavior, they refused all food offered and died four days after hatching.⁷ This is a common problem when trying to rear deep-sea fish larvae in captivity: the conditions, prey items, and environmental cues are so different from their natural habitat that survival beyond a few days is extremely difficult. Still, the study provided the first visual record of oarfish development from egg to larva, filling in a blank that had persisted for as long as the species had been scientifically described.

The practical problem for understanding oarfish population health is that we know almost nothing about where they spawn, how often they reproduce, how many eggs a female carries, or how many larvae survive to adulthood in the wild. Without these fundamentals, estimating population size or trends is essentially impossible with current data.

What Oarfish Eat

Examining the stomach contents of oarfish requires actually getting your hands on a fresh specimen, which, given everything discussed above, does not happen very often. The Taiwan study that documented a young oarfish captured alive in shallow water also analyzed its stomach and found 38 individual larval fish belonging to three species, which made up the vast majority of the prey items, along with six crustaceans from three different species.⁴

This diet of small fish larvae and crustaceans fits with the oarfish’s anatomy. They have tiny, toothless mouths that are not built for catching large prey. Instead, they likely filter or pick small organisms from the water column, swimming slowly through dense patches of zooplankton and larval fish. Their vertical swimming posture, often observed in ROV footage where they hang head-up in the water column, may help them scan above and below for prey concentrations. The limited dietary data available suggests oarfish are planktivores, more like gentle grazers of the deep water column than the fearsome predators their size might imply.

Conservation in the Dark

Oarfish are not currently listed as threatened or endangered by any major conservation body, but this is not because their populations have been assessed and found healthy. It is because no one has enough data to assess them at all. The International Union for Conservation of Nature categorizes species as “Data Deficient” when population information is insufficient for even a rough determination, and oarfish fall squarely into that gap.

There is reason for at least some concern. A study published in Nature demonstrated that five species of deep-sea fish in the northwest Atlantic declined so steeply over a 17-year monitoring period that they met the criteria for being critically endangered.⁸ Those were commercially fished species with at least some survey data. Oarfish are not commercially targeted, which likely protects them from the most direct form of human pressure, but they share the same deep-water habitat that is increasingly affected by deep-sea trawling, underwater noise, pollution, and changing ocean temperatures. If deep-sea fish populations in general are more vulnerable than previously recognized, oarfish could be declining without anyone knowing.

The absence of evidence is not evidence of absence, and for oarfish, the absence of data is profound. We cannot say how many exist, whether their numbers are stable, or what threats matter most. What we can say is that every species documented at mesopelagic depths faces a monitoring gap that makes terrestrial conservation look luxuriously well-informed by comparison. For an animal this iconic, the lack of basic population knowledge is striking, and it means that the true answer to “how rare are oarfish” is one science cannot yet give with any confidence.

1
Journal of Asia-Pacific Biodiversity. Taxonomic review of the rare oarfish Regalecus russellii (Regalecidae: Lampriformes) from Korea using morphological and molecular methods
2
PubMed Central / Journal of Fish Biology. Five in situ observations of live oarfish Regalecus glesne (Regalecidae) by remotely operated vehicles in the oceanic waters of the northern Gulf of Mexico
3
Thalassas: An International Journal of Marine Sciences. Where and when has the rare Fish Species Regalecus glesne been Found in the Mediterranean so far?
4
Zootaxa. Stomach content analysis of young Russell’s oarfish (Regalecus russelii) from Taiwan, and a report on an unusual case of predation
5
Bulletin of the Seismological Society of America. Is Japanese Folklore Concerning Deep‐Sea Fish Appearance a Real Precursor of Earthquakes?
6
Journal of Asia-Pacific Biodiversity. Taxonomic review of the rare oarfish Regalecus russellii Regalecidae Lampriformes from Korea using morphological and molecular methods
7
PubMed Central. First observation of larval oarfish, Regalecus russelii, from fertilized eggs through hatching, following artificial insemination in captivity
8
Nature. Deep-sea fishes qualify as endangered