Apr 30, 2014 I Brent Swancer

Giant Mystery Fish of Japan

We’ve all heard big fish stories. It seems that we all know someone who knows someone else who caught a fish “Thiiiiis big,” or have heard about the “one that got away.” Japan also has a large number of reports of what can only be described as giant fish haunting its lakes and rivers.

Let’s take a look at some of the enormous mystery fish that call Japan home.

The Namitaro

Takanami Pond, in Niigata prefecture, Japan, lies 540 meters (1,722 feet) above sea level in a wilderness area. It is known for its pristine wilderness, camping, and hiking trails. It is also allegedly home to an enormous fish locals affectionately refer to as the Namitaro.

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Takanami Pond

The fish is said to be between 2 to 4 meters (6.5 to 13 feet) in length and covered in large scales. The Namitarou rarely comes to the surface, but is known to startle people strolling along the pond from time to time. Fishermen have also claimed on occasion to have caught the beast, only to have it break their lines.

One report of a more close encounter described how a man had entered waist high water in the pond to retrieve something he had dropped. As he blindly felt through the murky water and silt at the bottom, his hand came up against what he took at first to be a large log at the bottom. It was only when this “log” suddenly began to swim away that he realized it was some incredibly large fish. The mysterious fish was so large and powerful that the sweep of its tail as it swam off actually bumped into the man and knocked him down. The man described being terrified, and quickly exited the water to see a large wake as whatever it was sank into the depths.

The pond is an odd place for such a large cryptid, as it is small and shallow, being only 13 meters at its deepest point. In addition, the area is quite popular for its hiking and camping, and there are many campgrounds, parks, shops, and restaurants in the vicinity of the pond.

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Sculpture of the Namitaro near the pond.

The Namitaro has become somewhat of a legend in the area, and most people who pass through pause at the pond hoping to catch a glimpse of the elusive creature or the large wakes and waves it is said to produce as it cruises under the surface. These waves are so well-known that indeed the name Namitaro is a combination of the Japanese words for “wave,” nami, and Taro, a common Japanese first name, sort of like “John” for Westerners.

It has been speculated that the Namitaro could be a specimen of a large species of Asian carp, such as the grass carp or black carp, that has somehow been released into the pond and grown to epic proportions. These species of carp get to very large sizes that are comparable to what people have seen in the pond. The black carp, for instance, can reach up to 6 feet in length and weigh over 200 pounds. An even larger species, the Siamese giant carp, can get up to around 10 feet long.

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Siamese giant carp

If you are ever in the area, keep your eyes open and perhaps you will see the Namitaro for yourself. Or you may want to drop a line in. You never know what you might catch.

Giant Trout of Hokkaido

If fishing is your game, perhaps you’d like to venture to Hokkaido’s Lake Shikotsu. There is a chance you will catch one of the mysterious denizens of its depths, the mysterious giant trout of Lake Shikotsu.

The lake is a caldera lake, with an average depth of 265.4 meters (870 ft) and is categorized as the 8th largest lake in Japan by surface area. Lake Shikotsu is well known for its excellent fishing, being home to the Japanese record brown trout, which was 93.5 cm (3 feet) long and 13.5 kg (30 pounds). That’s big, but perhaps the most famous attraction here are the mysterious gargantuan trout said to inhabit the deeper parts of the lake.

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Lake Shikotsu

Fishermen have long reported seeing what they describe as giant trout estimated to be around 2 meters (6.6 feet) or more in length out in the deep water areas of the lake. One boat full of fishermen were astounded when they saw a whole school of the enormous fish near the surface, ranging from 1.5 meters to 3 meters in length.

Another fisherman claimed to have caught and reeled in a trout he described as a whopping 3.5 meters (11.5 feet) in length. When the fish was pulled near the boat, the fisherman and his cohorts were totally blown away by the sheer size of the catch. It was unlike anything they had ever seen in all of their years fishing on the lake. As the fishermen stared in disbelief, the giant fish broke the line and darted off into the depths.

Although the lake is home to many salmonoid species such as brown trout, rainbow trout, and red salmon, none of these can account for the vast sizes described for the mystery fish. The most common theory is that people are seeing rogue specimens of Sakhalin Taimen (Hucho perryi), one of the world's largest salmonoid species, which can reach lengths of up to 2 meters (6.6 feet) and weights of 100kg (220 pounds). Taimen are not known to inhabit the lake, but they are found in Hokkaido. If there is a population that somehow got into the lake, then it may account for these reports of giant mystery trout.

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Sakhalin taimen

The giant trout of Lake Shikotsu are only ever seen in the deep waters of the lake and have not been seen from shore, so sightings are relatively rare. Some have suggested launching expeditions in search of the giant trout, so perhaps at some point we will have a better idea of what we are dealing with here. Until then, it is a mystery.

The Takitaro

In Yamagata Prefecture on Honshu island, Japan, there is a small, isolated body of water by the name of Otori-ike 大鳥池, (literally translated as Otoro Pond), which lies high in the mountains, 1,000 meters above sea level. Despite its Japanese name (“ike” means “pond”), the limnology of Otori-ike is not that of a pond. It is in fact a lake, created when a landslide blocked off a mountain stream long ago. The lake is 3.2 kilometers (2 miles) around and 68 meters (223 feet) deep at its deepest point.

Located within Yamagata’s largest virgin forest, Otori-ike is known for the area’s stunning natural beauty, and is a haven for hikers. The lake is also known to be the haunt of a mysterious giant fish, known locally as the Takitaro.

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Otoro Pond

The Takitaro are said to be enormous fish capable of reaching sizes of up to 3 meters (10 feet) long. Locals have long told of seeing these giant fish in Otori-ike, and the creatures are well integrated into the folklore of the area. Takitaro were once claimed to have the ability to bring in storms, and the sight of one was said to mean that a storm was imminent. The fish were often said to attack small boats, and were blamed for the occasional disappearance of fishermen.

One old story tells of a boat that was pulled under the waves by a Takitaro as horrified villagers looked on. Takitaro were also believed to snatch deer and other animals from the lakeshore. There is one account that describes a Takitaro carcass washed up on shore that when cut open revealed the remains of a deer. Residents of the area have claimed to even catch Takitaro on occasion and in fact the fish are widely believed to be good eating.

A modern report of such a catch occurred in 1917, when workers investigating a floodgate managed to capture a fish that measured 150 cm (5 feet) long and weighed 40 kg (88lbs.). The men reportedly ate the fish, and described its meat as being quite good. Other specimens have reportedly been captured throughout the 20th century as well. Several of these captured specimens have been described as being anywhere from 160 cm (5.3 feet) to 2 meters (6.5 feet) long.


Stories abound of fishermen encountering these monstrous fish right up to the modern day, with accounts of mysteriously mangled nets and fishing poles violently yanked or broken by something very large and strong. One report spoke of something that looked like a “moving log” that was witnessed to bowl right through a fishing net. According to the eyewitness, the fish was almost 2 meters long and had what appeared to be a thick layer of fat.

Other reports are somewhat more frightening. One eyewitness reported seeing a huge dark shape under the surface methodically swim about sucking ducks under the surface. The mystery monster would devour one duck, then cruise around and do it again over and over. All told, the creature was reported to have devoured at least five ducks before sinking into the depths. Another account describes a rowboat being violently rammed by something huge in the water. The terrified eyewitnesses claimed that the boat was close to capsizing when whatever it was left them alone and disappeared.

While locals have been aware of these mysterious fish for a long time, perhaps the sighting that single handedly brought the Takitaro into the limelight and to mainstream consciousness in Japan was made by four mountain climbers in 1982. Tomoya Sawa, Kenzo Matsuda, I. Onodera, and Masakazu Sato, were hiking along Otori-ike’s nearby Nao Ridge when they saw several huge fish estimated as being 2 meters (6.5 feet) to 3 meters (10 feet) long swimming through the lake’s crystal clear water.

This sighting was a sensation all over Japan, and was plastered over most major newspapers. The tale of giant fish dwelling in this picturesque mountain lake fired up the public imagination. Only adding to this fervor was footage captured by a group of TV reporters investigating Otori-ike in October 1983 in the wake of this sighting. The reporters’ footage shows three huge shapes swimming under the surface of the water.

Sign in the vicinity of Otoro-ike featuring the Takitaro.

In response to the incredible amount of attention this sighting and the subsequent footage generated, a scientific expedition was mounted to the lake in 1985 in the hopes of obtaining evidence of the Takitaro. Scientists conducted a thorough search of the lake using sonar equipment, during which they made some peculiar finds.

In the deeper parts of the lake, sonar picked up readings at a depth of 30 to 40 meters (98.5 to 131 feet) of what appeared to be fish much larger than any known to inhabit the area. Although the exact type of fish could not be determined, these curious sonar images seemed to confirm that something very large and mysterious was indeed lurking in the depths.

Gill nets laid out by the team also brought up some unusual findings. The nets captured several Dolly Varden trout (Salvelinus malma malma), which were much larger than usual for the species, although not nearly as large as the alleged Takitaro. In addition, Dolly Varden are represented in Japan by a landlocked subspecies that only inhabit the northern island of Hokkaido. They were not previously known to be in Otori-ike at all. Whether or not these super sized Dolly Varden were connected in any way to the giant Takitaro, they nevertheless represent an unusual finding.

Another theory is that perhaps the fish are a relic population of an ancient, extinct species, or even an unknown fish species that was trapped when the landslide formed Otori-ike from a stream long ago.

The Dragon Fish

During Japan’s Meiji period (1868 to 1912), there were frequent reports of a very large, reptilian looking fish that was typically referred to as the Ryuu Gyo, or Dragon Fish. The Dragon Fish was usually described as being around 2.4 meters (8 feet) in length, and covered in bony, armored plates. It was quite reptilian in appearance, and was said to have a head like an alligator, but was clearly described as some type of fish.

Reports of the day abound. One occurred in 1873 in present day Ibaraki prefecture. In this case, a strange giant fish 8 feet long and covered in prominent scales was caught by villagers. Those who examined it were stumped as to what it could be, and the case was widely reported in the news publications of the time.

In 1875, fishermen in Watarai province noticed that something was destroying their nets. An active hunt for the culprit was carried out and after an extensive search, a large Dragon Fish measuring 3 meters (10 feet) in length was captured. Again, the fish was described as being covered in bony protrusions and the specimen was said to have the head of an alligator. Some adventurous locals tried to eat some of the fish and described it as tasting rotten and foul.

From the descriptions it seems like there’s a fairly god possibility that the Dragon Fish were perhaps sturgeon. These large fish reach sizes consistent with the reports, have what could be said to be a crocodilian appearance, and are also covered in bony plates.

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In addition, an artist's depiction of a Dragon Fish from the era bears a remarkably strong resemblance to a sturgeon. Sturgeon are not native to Japan’s Honshu island, where these reports of Dragon Fish originate, yet perhaps some were imported and found there way into the wild.

Sturgeon would have been a very unfamiliar sight to rural people at the time, and thus could have easily been reported as monster mystery fish. Since the Dragon Fish is only known from reports during the Meiji period, perhaps we will never know what they were.

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Artist's depiction of a Dragon Fish


Mystery River Rays

The Nagara River of Gifu prefecture, Japan, has been the source of several sightings of what appear to be giant, river going rays.

The first report surfaced in 1986 in Hashima City, Gifu, where an eyewitness described seeing a ray-like fish with “wings.” The mysterious fish was estimated as being 2 meters (6.6 feet) long and 1 meter (3.2 feet) wide from wingtip to wingtip. It was said to appear to be “flying” through the water. Although only the silhouette of the creature was seen, the witness, a long time resident of the area, said the shape of the creature was very much like that of a ray and unlike anything he had ever seen in the river before.

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Nagara river

In another case, a group of elementary school children on a field trip saw a large ray in a clear water pool of the river. The children excitedly called to their nearby teacher, who came to investigate. The teacher went on to describe the ray as having a 2 meter (6.6 feet) wingspan. It appeared to be just leisurely gliding through the pool. They watched the curious fish for around ten minutes before it glided off.

A few other sightings of the mysterious fish have popped up over the years, all describing the same distinctive “winged” shape of the original sighting.

Although Japan has no such species, there are very large river rays that do exist in other parts of Asia.The Mekong River giant freshwater stingray of Southeast Asia can be 5 meters (16.4 feet) long and up to a whopping 600 kg (1,300 lbs). Could there be some similar type of large, freshwater ray remaining undiscovered in Japan?

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Mekong River giant ray

There are only a small handful of sightings of this enigmatic river creature, so it seems likely we may never know for sure.

Giant Eels

Various locations in Japan have had reports of huge eels far larger than any known native species.

Workers doing construction on a floodgate on the Edo river reported coming across enormous eels measuring 2 meters (6.6 feet) long. According to the account, four of the eels were spotted and some of the workers even attempted to capture one, as the eels appeared to be rather lethargic and slow moving. They were unsuccessful as they did not have the equipment to properly catch one. Upon returning to the scene later on with the tools they needed, they found that the mysterious giant eels were nowhere to be seen.

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Artwork by bennyb92 at Deviantart

Another account comes from Lake Biwa, which is in Shiga Prefecture, and is the largest freshwater lake in Japan. In the 1980s, there were several reports of giant eels inhabiting the lake.

One such sighting was made by a large group of people aboard one of the lakes many pleasure boats. Startled ferry passengers reported seeing several very large eels swimming at the surface far from shore. The eels were described as being around 3 meters (around 10 feet) long, and a silvery blue color. The eels appeared to be leisurely gliding along beside the boat and were observed for around 15 minutes before moving off out of sight.

A fisherman on the same lake reported actually hooking and reeling in an eel that was reported to be around 8 feet in length. In this case, the eel was kept and eaten. Another fisherman on the lake reported seeing a similarly sized eel rooting through mud in shallow water near the shore.

There are some incredibly large eels around the world, perhaps the largest being species such as the longfin eel native to New Zealand, which can reach nearly 2 meters in length, as well as the similarly sized giant mottled eel native to Indo-Pacific habitats.

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Longfin eels

Is it possible that giant eels reports are of out of place exotic species in Japanese waters, or is there perhaps a new as yet undiscovered species of large eel in Japan?

With so many different giant fish reports from Japan, it seems that it may be worth bringing your fishing gear along if you are ever in the Land of the Rising Sun. You just may bring back a big fish story of your own.

Brent Swancer

Brent Swancer is an author and crypto expert living in Japan. Biology, nature, and cryptozoology still remain Brent Swancer’s first intellectual loves. He's written articles for MU and Daily Grail and has been a guest on Coast to Coast AM and Binnal of America.

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