In March this year, I spent a week in Taiwan as a guest of the Taiwan Fisheries Agency. My hosts had laid on a relentless daily schedule that took in a complete circuit of the island nation, visiting nearly all the major commercial fishing ports, including Taitung on the Pacific Ocean, Tainan and Kaosiung on the South China Sea, Suao on the East China Sea and some smaller ones as well.

In addition, a visit was arranged for me (in the interests of JT readers) to Sealink International Co.’s eel-culture farm at Xuejia in the southwest part of the island.

Since Japan consumes 70 percent of the freshwater eels (unagi) worldwide, of which it gets 80 percent from China and Taiwan, this was too important and interesting an chance to miss. So, after an early morning visit to An Ping fishing port in Tainan, we headed inland over unpaved country roads — seemingly with duck farms in every direction — until we finally reached Xuejia.

According to Wen-chien Chen, the company’s president, all the eels raised on the farm — after having been captured as fry spawned in the North Pacific off the Marianas Islands — are exported to Japan. To get there, the eels are airfreighted live, packed in ice at 5e_SDgrC, when they are between 12 and 18 months old and weigh 200-300 grams. Most of the 200 tons, valued at around ¥175 million, that the company shipped in 2012 were delivered directly to markets in Toyohashi, Aichi Prefecture, and nearby Hamamatsu, Shizuoka Prefecture — where Lake Hamana is traditionally considered home to the best-quality unagi.

Sealink raises their eels from fry (baby eels). Although some fry were purchased from mainland China in 2012, this year the farm plans to use only wild-caught ones spawned in the North Pacific off the Marianas Islands — a controversial practice that in 2010 led Greenpeace International to add the Japanese eel (Anguilla japonica) to its seafood red list, which comprises species that are commonly sold in supermarkets but face a very high risk of being sourced from unsustainable fisheries.

The eels are raised in man-made ponds, filled by rain water, aerated with pumps and covered with netting to keep out predator birds. Naturally carnivorous, they are fed a mixture of dough and fishmeal, though Sealink is at pains to point out it makes every effort to raise the eels in as natural an environment as possible.

So why are unagi so valuable in Japan? Well summers, especially on the Kanto Plain where the Tokyo-Saitama-Yokohama mega-conurbation is located, are pretty hot and, far worse, extremely humid. The Japanese term mushi atsui (literally, “steaming hot”) accurately describes that weather. Unagi, or freshwater eel (Anguilla japonica), is eaten throughout that season, but especially on a day called Doyo no Ushi no Hi (Midsummer Day of the Ox), which is considered to be the hottest day of the year and quite often actually is.

Doyo no Ushi no Hi is determined by the Chinese-derived lunar calendar, and in the Western calendar is falls in late July or early August — this year, it’s July 19. About 10 days before the great event, when everyone is meant to counteract natsubate (summer fatigue) by scoffing this food rich in supposedly restorative constituents, whole sections of supermarkets in Japan are set up with stalls selling grilled unagi from various sources and in various forms — of which by far the most popular is kabayaki (glaze-grilled unagi).

To create this delicacy, the backbone of the eel is removed, rendering fillets, as eels have no ribs. The fillets are grilled over charcoal while being basted with kabayaki sauce, which is made from equal parts soy sauce and sweet mirin (cooking sake), with a generous amount of sugar added — about ¼ cup of sugar to 1 cup of liquid is common. Then, as the unagi fillets are being grilled, the fat drips onto the hot charcoal, creating smoke that adds flavor to the kabayaki sauce.

Several popular dishes are made using glaze-grilled unagi. Unadon (or unagi donburi), which is simply cut-up portions of unagi-no-kabayaki served over a bowl of rice, with the sauce penetrating and flavoring the rice, is perhaps the most usual presentation. Other ways of serving this succulent treat include unagi sushi, which is sold both packaged in shops and on plates at sushi shops, especially at kaiten zushi (revolving sushi) bars; unagi bentō, which is a simple meal of an unagi fillet on rice served in a lunch box; and unagi kabayaki on skewers, usually sold right off the grill by street vendors.

Japanese people eat around 100,000 tons of unagi every year — but is it really good for the body in high summer? The answer is definitely in the affirmative, since it’s high in protein and vitamins A, B1, B2, D and E, all of which help restore energy lost in the summer heat. Vitamin B1, especially, is lost as we sweat. Unagi is also high in DHA and EPA, the so-called “good cholesterols” which help to clean the blood and prevent high blood pressure.

That said, there have been problems with unagi imported from mainland China, which have been found to contain the anti-bacterial chemical malachite green, which is banned in Japan for being carcinogenic. This is an economic as well as a health problem, since the vast majority of unagi sold in Japan comes from fish farms.

Of the 20 percent of unagi produced in Japan, less than 1 percent consists of wild eel caught by fishermen from Kumamoto and Kochi prefectures in the southern islands of Kyushu and Shikoku, respectively. The rest is farmed in Aichi, Gifu and Shizuoka prefectures.

Those unagi from Hamamatsu, on Lake Hamana, typically sell for more than double the price of the imported product. To further complicate the situation, though, some slippery dealers have recently been arrested for falsely labeling imported Chinese eels as Japanese ones from Hamamatsu.

Traditionally, Chinese eel farmers imported newborn eels, called elvers, or glass eels (because they are transparent), from Europe, mainly France and Spain, but since they were classed as endangered by the European Commission in 2007, their export from the European Union has been heavily restricted. As a result, Japanese scientists, mostly from the University of Tokyo’s Ocean Research Institute, have stepped up efforts to locate the eels’ ocean spawning area.

Research began as early as 1967, when 60-mm glass eels were caught off Okinawa. Then in 2005, 7-mm specimens turned up near Guam. Finally, fertilized eel eggs were found between 150 and 200 meters down adjacent to the Marianas Trench, east of Guam and the Marianas Islands, in the summer of both 2008 and 2009.

Spurred on by those finds, scientists at the University of Tokyo’s Atmosphere and Ocean Research Institute collected more eggs and larvae (leptocephali) in 2009 and 2011, and so could estimate at what depth and water temperature successful adult spawning and egg/larval development occurred.

In turn, this information can be used in aquaculture efforts attempting to provide glass eels for Japanese eel farmers through captive spawning and larval rearing — so almost eliminating the threat to wild populations.

Researchers believe that eels spawn multiple times during the summer breeding season, and then die. Afterward, the larvae migrate thousands of kilometers to the home rivers of their parents before returning about seven years later to spawn and die in the same part of the ocean where they were born.

Although unagi is most often associated with summer and with restoring energy to the body — some believe it boosts sexual vigor as well — it is available year-round, and there are unagi restaurants all over Japan featuring signs or banners with the hiragana symbol for “u” drawn to resemble the shape of a wriggling eel. The invariable main dish, unadon, is usually served with Japanese pickles (tsukemono), Japanese pepper (sanshō) as a condiment to sprinkle over the fish, and kimosui, a clear soup containing eel liver, which is also said to be highly nutritious.

So while the notion that eating unagi boosts sexual energy can be backed up to some extent by science, other beliefs about eels are even harder to test. For instance, in Japan, Jinshin-Uwo, a giant namazu (catfish), is a mythological creature said to carry the country on its back and cause earthquakes when it shakes its tail. In some versions of the legend, Jinshin-Uwo is a freshwater eel.

According to the Gale Encyclopedia of Occultism and Parapsychology: “Eels figure in the folklore of many countries. The Egyptians worshiped the eel, which their priests alone had the right to eat. In Polynesian, Melanesian, and Indonesian stories, men are sometimes transformed into eels. In the Philippines, eels were believed to be the souls of the dead.”

So, whether you care to believe in sacred eels, were-eels or zombie eels, you can believe that eating grilled unagi this summer will delight your taste buds, benefit your health and boost your vital energy.

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