Today, July 26, is doyo ushi no hi, which translates directly as “hot day of the ox” though the food that is traditionally eaten on this day is not beef but rather unagi (eel). So why isn’t it called unagi no hi? That’s a good question and one that isn’t easy to answer, since the idea originated many centuries ago in China, where the cycle of days was based on 12 rather than 7, and to help people remember the cycle each day was assigned an animal, in the same way that the old calendar groups years into cycles of 12 animals. Somehow over time the day of the ox came to represent the high point of summer, meaning the hottest day of the year, which was pinpointed as being 18 days before the first day of autumn according to the old calendar.

This year that day falls on July 26, which won’t make sense to anyone except people with an interest in arcane Asian astrology. It certainly doesn’t explain why people eat unagi on this day. There are many theories, one of which is that both “ushi” and “unagi” begin with the “u” sound, though the hypothesis that seems to be the most accepted is that some time during the Edo Period (1603-1868) fishmongers got together to promote eel because it didn’t sell as well as other fish and hit on the idea of saying that it boosted stamina during the dog days of summer. In other words, it was a marketing ploy, and just as American greeting-card companies effectively created Mother’s Day, these fishmongers hit on the proverbial hottest day of the year — doyo no ushi no hi — as a good day to promote eel sales.

The Japanese populace bought it, and ever since then unagi sales have been brisk on this day, despite the relative high price compared to other fish. The high value attached to unagi is another mystery and, again, seems to be more a matter of marketing than anything else. In recent years, there have been many scandals involving unagi distributors who have purposely mislabeled unagi from Taiwan or China as having been grown in Japan. Domestic eel commands a higher price, even though in many cases there’s absolutely no difference. The bulk of unagi sold in stores and to restaurants in Japan come from eel farms, and most of the farms, whether they are in Japan or China or Taiwan, get their fry from Japan.

It’s impossible to grow unagi from eggs because despite the fact that unagi is designated as a fresh water fish, it lays its eggs in the ocean. (Anago, another eel species that is a popular dish in Japan, live in seawater their whole lives.) Their life cycle is the opposite of salmon, which lay eggs in freshwater but live their lives in the sea. In fact, no one knows precisely where unagi lay their eggs, though the most common theory is some place in the vicinity of the Marianas. After hatching the fry make their way back to Japan waterways and are caught in nets. These fry are then sold to unagi farms where they are raised to adulthood.

You can also buy tennen (natural) unagi, meaning they are adult eels caught in rivers or lakes, and they are more expensive, usually by a factor of two, simply by dint of their lesser availability. Do they taste better? As with the difference between domestically grown unagi and foreign grown unagi, it’s a moot point and one that unagi wholesalers take advantage of to keep prices high. (It should be noted that more and more Chinese farms are getting their fry from Europe, which would seem to be a different species of eel.) But in any case, retail prices for domestic unagi are on the average 30 percent more than for foreign unagi, and according to a report I saw last night on NHK, this year about 80 percent of the unagi you buy in stores is from overseas, and prices are, on average, about ¥500 more than what they were last year owing to a 60 percent drop in catches of unagi fry. But true unagi lovers say the taste of eel has more to do with preparation than with origin, and thus another cost layer is added. It’s believed that the eel should be killed just prior to cooking, and “real” unagi restaurants keep tanks of live eels on the premises.

There’s yet another layer of cost that can only be explained by cognitive dissonance. Probably the most famous unagi restaurant in Tokyo is Obana, located near Minami Senju Station in Arakawa Ward, next to the old execution grounds. Obana doesn’t advertise, doesn’t accept reservations and doesn’t allow media coverage. Moreover, it only serves three unaju (grilled eel on rice) dishes, and the wait is long. Typically, there is a long line outside the closed gate before the restaurant opens for business at 11:30 a.m., and it only stays open until its supply of unagi for the day runs out. Because preparation is Obana’s hallmark, once you sit down you have to wait one hour for your meal to arrive, which gives them plenty of time to sell you as much beer as you can drink. So the usual wait time is at least two hours: one hour waiting on line, and one hour waiting at one of the 25 two-person tables. And the dishes are expensive: ¥3,000, ¥3,500 and ¥4,000 (pickles included but no soup). Is it better than other unagi restaurants? Probably, but as a friend of mine used to say, if you wait in line an hour to see a movie, you’ll probably think it’s better than if you didn’t wait at all.

In any case, it works as a backhanded marketing tool. On Saturday, two days before doyo ushi no hi, there were about 100 persons standing in 35-degree heat with no shade outside Obana 15 minutes before it opened. Unlike eel, the old Edo Period strategy still has legs, so let’s hope the theory about unagi boosting stamina isn’t the myth it seems to be.

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