Transcription
The ocean is 11 km deep at its lowest point. The further down we go, the less we know. And of all of it, every trench, every ridge, every square kilometer of seafloor, it remains by every measure the least explored environment on our planet. We've sent machines down there and every time we go down, we find something we weren't expecting. What lives in that place? We mostly don't know.
But sometimes the deep gives something back. An enormous silver body washes ashore. A shape that doesn't match anything in a textbook. Nothing like anything else anyone has seen in the ocean. Something out of a nightmare. This is the orefish. It lives in a part of the ocean we almost never see. And for most of human history, the only time anyone met one was when it surfaced dying or washed ashore already dead. Silver, enormous, longer than most people can actually imagine when they hear the number.
Medieval seafarers called it the sea serpent, a monster that could coil around ships and drag them under. In Japan, it became Ryugu Nsukai, a messenger from the Palace of the Dragon King, believed to appear before catastrophe. In the months before the 2011 earthquake and tsunami that killed nearly 20,000 people, dozens of these animals washed up on Japanese coasts. People remembered the legend and researchers are still arguing about whether there's anything to it.
See, for years, people got acquainted with the legend without ever meeting the creature. They would find the dead body washed ashore, listen to the legends of the sea serpent, yet they had no chance to observe the fish alive. But how can such a big creature swim under the water? What is its path? Why did it rise from the depths at all? These questions were left unanswered for ages. Not anymore, however, and the true story might even be more mysterious than the legend.
"My goodness, that's the biggest fish I've ever seen."
The orifish is the longest bony fish on Earth. Its name comes from the Latin regalis, meaning royal. For a long time, people believed the fish used its long pelvic fins like orars rowing itself through the water. That turned out to be wrong, but the name stuck. And honestly, once you see one, that name makes complete sense.
"Oh my god."
A body that can reach around 8 m and 272 kg. And like many deep sea fish, it may not stop growing in the clean way we expect from animals near the surface. Growth appears to continue for much of its life, which means an old orfish may not just be older, it may simply be longer. A horselike face, a flame red crest rising from the skull like a crown. A gelatinous silver body, no scales, just a mirror-like coating that reflects whatever faint light reaches it from above. And it doesn't swim horizontally like almost every other fish on Earth. It swims vertically. Head pointing up toward the surface, tail pointing down into the dark.
Nobody fully understands why the orfish isn't really one species. It's three, all in the family regal. The giant orfish and Russell's orfish, both in the genus Regalcus, and the more distantly related streamer fish, Agrastikus Parkery, which has been reported to produce a mild electric shock when handled. Whether the others can do that too, we still don't really know. And almost everything science has actually figured out about any of them comes from a single species, Regalus Glesny, the giant orfish. But here's the awkward part. Even that knowledge came almost entirely from dead bodies.
The first specimen was formally described in 1771 by a Danish naturalist named Morton Brun who found one washed up on a beach in Norway. And for the next two centuries, that was basically how science worked with this animal. Across every temperate coastline on Earth in all that time, fewer than 250 beachings have ever been documented. For a fish that can reach 8 m long, that number is almost impossible to believe. When one does appear, it's rarely a quiet event.
"This 18t long sea monster."
When these eerie fish show up, in 2013, an 18 ft orfish washed up near Catalina Island in California. It took 15 people to haul it out of the water. The reason these strandings are so rare isn't hard to understand once you know where the orfish actually lives. The twilight zone, 200 to 1,000 m below the surface. Little sunlight, not enough for photosynthesis, and below a certain point, almost total darkness. Pressure far beyond what the human body could survive without protection. And water so still, so completely without current that an animal living there for millions of years never had to develop any meaningful muscle mass. The orfish is, in a very literal sense, a creature of total stillness. Finding one alive down there is less like ocean exploration and more like trying to spot a single animal in the largest, darkest, most featureless habitat on the planet.
Long before naturalists got their hands on a body, sailors were already reporting something much more frightening. Teeth, ship attacks, a creature that could reach 56 ft long. The sea monster accounts written by Aristotle and Plenny the Elder are now thought to have been orfish encounters. The silhouette matches almost every historical sea description on record. When 19th century naturalists finally examined actual bodies with scientific attention, the teeth disappeared from the record. The monster became a fish. But the fundamental mystery didn't shrink with it. Because what the bodies couldn't tell us was everything that actually mattered. Where it spawned, how it navigated in total darkness, what it ate, or how long it lived. Those questions sat unanswered for 150 years. The only way to answer them was to find one alive at depth in its own world. And that turned out to be considerably harder than it sounds.
In the winter of 2014, more than a dozen fresh or fish washed up on the shores of southern Japan over the course of a few months. Not one or two, which would have already been remarkable. More than a dozen in good condition of varying sizes. For the first time, scientists had enough material to apply technology nobody had ever used on this animal before. The scans showed something unexpected. The brain of a giant orfish is only about an inch long. For a fish that can exceed 8 m, that ratio is one of the most extreme braintobody relationships of any vertebrate on Earth.
But the bigger discovery came from the X-rays. For decades, across every specimen ever examined, scientists had never once found nostrils on an orfish. The scans finally revealed them, tucked at the very front of the snout, opening forward, essentially inside the mouth. That means to detect any scent at all, the orfish has to swim with its jaws partially open, pumping water across those forward-facing nostrils. It seems to find smells by moving its head and following the strongest signal. For an animal with a brain barely bigger than an inch in a world with no landmarks and almost no light, that is still remarkable. And it raises a question those 2014 specimens couldn't answer. If the orfish is this sensitive to chemical signals drifting through the water, what happens when the chemistry of the deep changes? When something shifts down there in a way the animal has never evolved to expect.
A few years before the 2014 specimens, mostly in 2009 and 2010, around 20 orfish had been reported along Japanese shores. Then in 2011, the Tōhoku earthquake came. It was the most powerful earthquake ever recorded in Japanese history. The tsunami it triggered killed or left missing about 18,500 people. So naturally, people looked back at the fish. But scientists were careful. Correlation is not causation. An orfish usually comes to the surface when it is sick, injured, or dying, not because the ground is about to move.
Then in 2019, a team of Japanese researchers actually tested the idea. They compared hundreds of deep sea fish sightings with earthquake records across decades and they found one match, one strong earthquake within 30 days and 100 km of a fish sighting out of the entire data set. So the legend, at least in that form, did not survive the numbers.
But the 2014 findings made the story a little less simple because now we were looking at an animal that navigates almost entirely through chemical signals. An animal with nostrils built to detect faint changes in the water around it. And it lives above one of the most tectonically active regions on Earth. So, the question becomes slightly different. Could seismic stress create electromagnetic or chemical disturbances that move up through the water column? And could an animal built to detect tiny signals in the water register something like that? We do not know. Most of the evidence still points against the old legend, but the legend never fully disappeared. It just became less interesting than the animal itself.
In the summer of 2000, an oceanographic buoy was placed about 40 mi off the coast of Nice, France. Its job was simple. Measure the color of the ocean and send that data up to satellites. The buoy was anchored nearly 8,000 ft down, almost 2 mi below the surface. But the ocean does not really care what we build something for. The buoy's frame, its chains, and even the shadow it cast began to change the water around it. Algae grew on the surface. Small fish arrived. Then larger fish followed. Before long, this scientific instrument had become a small floating ecosystem. In spring, great white sharks were even seen circling it in slow rings, probably following the tuna that had been drawn there by everything else.
Every month, a diver went down to clean the buoys's optical sensors. And while cleaning them, the brushes created vibrations that traveled down the cable. In water, sound moves differently than it does in air. During the annual planktonic bloom, a living orfish rose out of the darkness below, possibly drawn by those vibrations. It was the first time in recorded history a human being had met one in the water. Out of more than 120 dives at that same location afterward, it only appeared two more times.
The problem with observing deep sea animals is fundamental. Scuba divers exhale constantly. And for animals that have never encountered a bubble in their evolutionary history, that disturbance is enough to send them straight back into the dark before you can study anything. The solution is a rebreather, a closed circuit breathing system that releases nothing into the water. With that and by timing the dives with the spring plankton bloom when more animals were moving through the water, a living orfish finally stayed long enough to be watched properly. It was nearly 5 m long, the largest ever observed alive in the Mediterranean.
What stood out immediately was the control. The orfish was not just drifting there. It was steering itself using the long dorsal fin that runs almost the full length of its body forward, backward, up, and down. The body itself stayed almost motionless, held vertically with the head pointing toward the surface. Only the fin moved like a long ribbon sending waves through the dark. It could control its position in a way that looked unlike almost anything else in the ocean.
For a long time, the assumption was that the orfish belonged mainly to the twilight and midnight zones. But ROV footage from the Gulf of Mexico recorded Regalus Glesny alive at depths as shallow as 39 m and as deep as nearly 493 m. This mattered because it was the first time an orfish had been encountered and recorded in its natural habitat, alive, swimming, and behaving normally. So, the animal once thought to live within a narrow band of the ocean turned out to move through a much broader vertical range than scientists expected.
During the buoy encounter, scientists finally had a living orfish close enough to sample. They gently collected mucus from its skin without harming the animal. It was the first genetic material ever taken from a living specimen rather than from a stranded body or a preserved sample. The skin itself was strange. It seemed almost completely insensitive to touch, smooth and scaleless, covered only with tiny raised bumps unevenly spread across the body and becoming more obvious toward the tail. The fish held its position and seemed largely unbothered.
But what the mucus revealed was even more surprising. The genetic difference between different orfish samples was around 10%. For animals that were supposed to belong to the same species, that was a large gap. Regalus Glesny dominates temperate waters around the world, including the Mediterranean. Regalus russeli dominates warmer Pacific waters, especially around Japan, Korea, and China. Their ranges are mostly separate with the only confirmed overlap off the southern coast of South Africa. And physically, they are almost identical. The main difference is tiny. Regalus Glesny has four to seven more crest rays on its crown than Regalcus rustelli. That is such a fine distinction that physical specimens alone could not clearly reveal the split. And even now the range is still being redrawn. In 2021, a regalicus forceli was caught off the western coast of Sri Lanka by a commercial tuna. It was the first confirmed record of the species in the tropical Indian Ocean, a range nobody had documented before.
Those old records of 17 m orfish, the ones that helped build the sea serpent legend and still sometimes appear in books and documentaries, are almost certainly not reliable. The longest specimens ever properly measured reach around 8 m. The larger numbers likely came from sailors estimating size at sea, photographs taken from angles that exaggerated length, and bodies stretched across decks in ways that distorted their proportions.
On one night dive at the buoy, researchers swapped their conventional white lights for ultraviolet lamps. Under UV illumination, two previously unknown bioluminescent organs lit up on the orfish's head, one on the forehead, one under the chin. Scientists think these serve two purposes. Pulling prey toward the mouth and making the animal visible to other orfish in a world with no other light source. The mirror-like silver skin appears to do something related but different. In the mesopelagic zone, krill, one of the orfish's main food sources, produce their own bioluminescent glow. The current hypothesis is that the orfish's reflective body simply mirrors that ambient krill light, making the fish effectively invisible to both the prey it's approaching and the predators watching from below. It can't produce its own light, so it borrows the light around it. Which raises a different question. How do these animals find each other across hundreds of meters of featureless dark?
When two orfish converged on the same buoy simultaneously, arriving as if responding to the same signal, the leading explanation was pheromones. Chemical messages released into the current, carried across enormous distances, detectable only by other orfish. Once they get close, a different system takes over. The orfish goes completely still and spreads itself wide, maximizing the reflective surface of its silver body, becoming a mirror in the dark. The red dorsal crest and pelvic fins, long dismissed as decorative, now look like signaling structures, communication tools for a world where sound and sight are almost useless.
Up to this point, every orfish the divers had seen carried the same strange damage. Sections of tail missing, scarred flanks, and blunt ends where the body seemed to simply stop. The obvious explanation was predation. Great white sharks had been seen around the buoys, so it was easy to imagine that something large had attacked them. But the evidence for that was weak. For an animal this big, the orfish has very few confirmed predators, and no documented shark attack has ever been recorded, and the only verified case involved pilot whales. So, the missing tails were probably not the result of an attack. The orfish was doing it to itself.
This is called serial autonomy. A lizard can drop its tail to escape, but the orfish does something different. It can shed parts of its own body behind the vent roughly 2/3 down its length. And it can do this again and again. The purpose does not seem to be escape. It seems to be energy conservation. By reducing its body length, the orfish lowers the cost of keeping itself alive, saving energy for the organs that matter most. It may be the only fish known to repeatedly amputate parts of its own body for metabolic reasons. And this may not be new behavior. The only known orfish fossil about 2.2 million years old shows the rear part of the body drawn inward in a way that looks consistent with the same process.
But the fossil could not tell scientists what the orfish was eating. Lipid analysis of the fin tissue did. The answer was krill. Specifically, bioluminescent krill from the mesopelagic zone. Their chemical signature appears in the orfish's flesh, and the red color of its fins and even its eggs comes from krill pigment. That also fits with how krill move. Every night, they rise toward the surface to feed, then sink back into deeper water before dawn. Orfish seem to follow that movement, drifting through krill aggregations with their mouths partly open. In those moments, they behave almost like filter feeders, taking in small prey and drifting organisms as they pass through the swarm.
Parasites added another clue. Stranded orfish contained nematodes linked to krill, and adult forms of the same parasite were later found in sperm whales. So, the orfish sits between krill and whales in the deep sea food chain, a mesopelagic link between some of the smallest and largest animals in the ocean.
In January 2019, two living orfish were caught in a commercial net off the coast of Okinawa. At just 40 m depth, one was already dead. The other was alive, but had lost its tail during capture. Before they were lost completely, researchers performed artificial insemination. It was the first reliable record of orfish reproduction ever documented. What that record revealed about the eggs themselves was almost as strange as everything else. Orfish eggs are buoyant, bright red, roughly 6 mm across, released into the open ocean to drift in the plankton with no parental care of any kind. The adult disappears back into the dark, and the eggs are left to the current.
Around 400 of them were fertilized and placed in a tank. To put this in perspective, most open ocean fish eggs hatch within 1 to 3 days. The orfish eggs took 18 days. After hatching, each larvae immediately did something that made no sense. Adult orfish swim vertically head up using their dorsal fin. The larvae spent more than half their time pointing downward and swam using their pectoral fins instead. They also carried a dramatically elongated dorsal fin filament averaging nearly twice their own body length whose function nobody has been able to figure out. And then despite having fully functional mouths, none of the larvae ate anything. Roifers, brine shrimp, fatty acid-enriched feed, nothing worked. Across the whole observation period, their mouths opened only six times. Within 4 days of hatching, all of them were dead. So, what do orfish larvae eat in the wild? We still do not know. Maybe something about the tank conditions was wrong in a way scientists could not identify. Or maybe the larvae feed on something so specific to the open ocean that nothing offered in captivity came close. Either way, the question is still open.
And it is not the only one. We do not know their spawning season. We do not know their maximum lifespan. Their geographic range is still being redrawn. Their communication system is still partly theoretical. Even their self-amputation behavior is known from only a handful of observations and one 2.2 million-year-old fossil. And this is the larger problem with the orfish. Almost every orfish that has entered the human record came to us by accident. Washed ashore, caught in a net, floating near the surface where it probably did not belong. We have almost never gone into its world and found it on our own terms. And if a fish this large, this recognizable, and this difficult to mistake can remain this unknown for so long, then the real question is not only about the orfish. It is about everything else down there that has never surfaced, never washed ashore, and never entered the light long enough for us to notice.
The deep ocean is the largest habitat on Earth. It helps drive our climate, shapes our weather, and contains the largest migration on the planet. More biomass moving up and down every night than the entire great migration in Africa. And yet, we have explored less of it than the surface of the moon. Whatever is down there is not waiting for us to find it. It is simply continuing in the dark the way it has for millions of years.