Japanese Freshwater Eel

Japanese tradition has it that eating unagi no kabayaki (freshwater eel that has been grilled and seasoned with a salty-sweet sauce) on a certain day (Day of the Ox, according to the Chinese zodiac) during the hottest part of the summer helps you beat the heat and fight off summer lethargy. Anybody who has spent some time in Japan during the summer knows exactly how debilitating the heat and humidity can be! The process of preparing, cooking and seasoning to create the perfectly grilled eel is much more difficult than it sounds, and it demands a professional skilled in the technique—this is not a dish that you would want to make at home! Eel is enjoyed in countries all over the world, but this elaborate method of preparation is seen only in Japan. As the weather heats up, let’s learn about these wonderful creatures, and see how deeply rooted and beloved they are, not only in Japan’s food culture, but around the world as well.

Eel: Fish of Mystery


The long and slender, cylindrically shaped freshwater eel is a fish, even though it might look more like a snake than a fish! At present, there are 18 confirmed kinds, or families, of eel. Eels are migratory fish, and they lay their eggs in the ocean. The young eels return upstream to freshwater where they mature (the opposite of salmon, who spawn in freshwater and mature in the ocean). They then descend back to the ocean where they breed. This journey has been made more difficult in recent years due to the building of dams and other water control structures and overzealous commercial fishing, environmental changes and pollution, and yet they still, heroically, follow their instinctively known path to perpetuate themselves. Eels spawn only during a very specific time period. They live in many areas; the tropics, temperature regions, and marshes, and they have been considered a food fish for thousands of years.

Beginning with ancient Egypt, eels have been revered as an incarnation or a messenger of a deity, most likely because of its admirable life force and survival skills—it is able to absorb oxygen through its skin as well as its gills; as long as the skin is moist it can survive, and it can wriggle up sheer precipices with only a bare minimum of moisture. Eels figure in many myths and folktales.

About 2,400 years ago, we find something written by the Greek polymath and philosopher Aristotle that attests to how mysterious the eel must have seemed at that time. He writes: “The eel spontaneously generates from within the mud.” Fast forward to the 1920s when research revealed that the European eels (which Aristotle was talking about), long thought of as freshwater fish, laid their eggs in the Sargasso Sea. And just a few years ago, in 2009, a research team from Tokyo University made history by successfully harvesting, for the first time, fertilized Japanese eel eggs from the North Pacific Ocean, along the west side of the Mariana Islands, finding the almost precise location of the eels’ spawning ground. There is, however, still much more of the eel’s life and habitats that remain a mystery to us.

Eel in the World’s Food Cultures

Eel in the World’s Food Cultures

When did eel start appearing on the world’s dinner tables? The oldest mention of eels is found in documents from ancient Greece, dating about 350 BCE, and after that, there’s mention of the fact in records from ancient Rome that eel was enjoyed there as well. At present, eel soups, stews and other dishes are enjoyed in the whole of Europe, the Far East, New Zealand and Australia. Well-known dishes include Eel Matelote from France, eels simmered in red wine; Spanish Angulas, young eels eaten with garlic and olive oil, and English jellied eels. Smoked eel sandwiches are popular in northern Europe and Scandanavia. During the Christmas season in Italy, it is traditional to eat the large eels called capitone fried or roasted, and in Comacchio, the ancient canal city of northern Italy, famous for being a large fishing ground for eels since the Roman Empire, there is a spectacular Eel Festival every year. Here in the U.S., prior to the Civil War, European immigrants ate eel, but nowadays it rarely, if ever, graces the table of most homes.

Eel in Japanese Food Culture

While we know that eel was eaten as part of the day-to-day diet in ancient Japan from the discovery of eel bones in the shell mounds of the Jomon period, approximately 5,000 years ago, it’s not clear how it was prepared. In poems from the Manyoshu, a collection of 31-syllable poems compiled from near the end of the 7th century to the end of the 8th century, we read that one should eat unagi to combat the summer heat, and from this we understand that starting thousands of years ago, the Japanese believed eel to have nutritionally fortifying and strengthening properties. The unagi written in the Manyoshu was steamed and seasoned with salt.

The first documented appearance of unagi no kabayaki in Japan was in 1399. This kabayaki was either eel sliced into thick round discs and grilled, or whole small eels which were skewered and then grilled. The appearance of the whole eels on skewers had a resemblance to cattail reeds, called gama, but which could also be pronounced kaba, and thus they came to be called kabayaki—literally grilled cattail reed. This early unagi no kabayaki was eaten with salt or vinegared miso.

About 200 years later in the early 1600s, there was an abundance of eels near the city of Edo (the old name for Tokyo) in the many low-lying wetlands which formed thanks to the dredging and reclamation of Tokyo Bay. Chunks of grilled eel were sold from vendor stalls as inexpensive and nutritious snacks for mainly the blue-collar crowd, similar to when soba first appeared in Edo. Until about the middle of the Edo period, it was considered rather low-class food; the thick, round chunks were not very visually appealing, they were difficult to cook through to the center, and because of this the meat retained too much of its natural oils which resulted in an unpleasant muddy odor. At this point in time unagi was considered nowhere near the delicacy it is regarded as today.

Unagi no Kabayaki As We Know It

One hundred years later, around 1700, the ikada style, or raft style, was invented in the Kanto region (an area that covers Tokyo and other nearby metropolitan areas). This method of preparation, a style still used today, is to cut open the eel lengthwise along the spine, debone, remove the head and fins, and cut in half crosswise. The meat is then pierced horizontally with several skewers giving it the appearance of a small raft. After the initial grilling over charcoal, the eel is steamed to remove excess oil, then grilled once again. The end result is tender, soft, melt-in-your-mouth wonderfully flavored fish. The mainstream seasonings at this time were still salt, miso and vinegar. This new way of cooking gave eel’s status a big boost, and its popularity began to fan out among a bigger audience.

The use of grilling eel with the salty-sweet soy sauce based sauce that is used today started at the end of the Edo period as a result of the development of koikuchi, or dark, soy sauce, in the Kanto area around 1750. Up until then, the soy sauce was from the Kansai region (the southern central area of the main island, to the west of the Kanto region, and includes Kyoto and Osaka), called usukuchi, and it was lighter in color and taste, yet saltier than koikuchi. The stronger flavored richer tasting koikuchi was more to the liking of the people living in Edo, and its use soon overtook usukuchi.

With the development of koikuchi soy sauce, it was only a matter of time before a delicious tare, or dipping sauce, to season the eel was concocted, creating what was considered by many to be the perfect flavor complement to the richness of the eel. This sauce was a mixture of koikuchi, mirin, sake and sugar, and it was boiled together, then reduced a bit to concentrate and mellow the flavors. Eel’s popularity soared, extending from its original blue-collar audience to those in the upper crust. Who knew unagi could be so delicious? Unagi no kabayaki shops cropped up all over metropolitan Edo, and it became one of the four main food cultures of the city, the other three being sushi, tempura, and soba.

Eel, a Nutritional Gold Mine

Eel is replete with high quality protein, Vitamins A, B1, B2, D and E. It is also rich in zinc and calcium, and the unsaturated fatty acids DHA and EPA. The slippery gel-like substance on eel skin (to be slippery like an eel is based in fact!) is called mucin, and it is important in protecting the gastro-intestinal mucous membranes. Nutritionally rich eel is can help you recover from fatigue, promote a healthy and sound appetite and increase all-around energy levels.

The unagi no kabayaki created during the latter half of the Edo period hasn’t changed much, and remains as popular as it ever was. Modernization has seen the use of machines to facilitate preparation of the dish in some shops, but there are still quite a few establishments of long-standing that continue to prepare it by hand, using the same methods generation after generation. This year, summer’s Day of the Ox falls on July 22nd, and many of us look forward to enjoying this traditional dish. But we should note that in recent years, due to climate change and certain fishing practices, there has been a reduction in the amount of eels harvested. Let’s help find a way to conserve and responsibly enjoy with gratitude this precious resource, which has a long and deep-rooted history in Japan and other countries, so we can continue to enjoy it for the years to come.