This year, doyo no ushi no hi, the "day of the ox," falls on July 29 in accordance with the old Chinese calendar. Counterintuitively, Japanese people don't celebrate the day by eating beef but rather eel, because, supposedly, eel, or unagi, helps maintain a person's stamina during the hottest days of summer. But it should be noted that the custom of eating eel is commercial in origin. According to legend, the tradition started in the 18th century in Hino, Western Tokyo, where nobody ate eel because the fish was a kind of local deity. An inventor named Hiraga Gennai came up with a publicity campaign to get people to eat unagi on doyo no ushi no hi because both ushi and unagi start with the "u" sound. The campaign worked, and now everybody eats unagi on doyo no ushi no hi. Well, maybe not everybody, but enough to drive Japanese eel to the brink of extinction.
Japanese eel for consumption are caught in the wild as fry and transported to eel farms throughout Asia. Eel is now on the International Union for Conservation of Nature's endangered red list, and so the environment ministry made the same designation on its list of at-risk species. However, this information has been tempered somewhat lately by media reports saying that the eel catch was higher this past year, thus driving the price of imported eel, mainly from China and Taiwan, down considerably. Consequently, eel dishes on the 29th may be cheaper in some places than they were last year.
Unagi fans will see this as good news, but it isn't. The reason eel is on the endangered list is that Japanese people catch and eat too much of the fish, which wasn't the case before the mid-1980s, when eel was considered something of a delicacy eaten only on special occasions. In other words, the cheaper the eel, the more likely eel stocks will be decimated.