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News Navigator: Has the number of juvenile eels fallen?

In this file photo, an eel filet is grilled during the high summer consumption period in Tokyo's Kita Ward, on July 25, 2017. (Mainichi)

The Mainichi Shimbun answers some common questions readers may have about the declining population of eels, particularly juveniles known as "shirasu unagi."

Question: Is it true that there has been a radical decrease in the number of shirasu unagi?

Answer: The majority of adult eel, or "unagi," in the Japanese market are shirasu unagi caught off the coast of Japan and other areas that are then farm raised to maturity. From November to the end of December 2017, only 0.2 tons of shirasu unagi filled marine farming ponds -- a shocking 3.4 percent of the 5.9 tons that were being artificially raised during the same period the previous year. Apart from Japan, China and Taiwan are also reportedly seeing a drop in the amount of shirasu unagi caught -- a staggering 1 percent of the previous year's yield.

Q: So we can't eat eel anymore?

A: According to the Fisheries Agency, there are two methods for raising eels: single year cultivation, which begins early from November to the end of January and takes roughly half a year to complete, and yearlong cultivation, which takes a year and a half to raise eels caught between February and April to adulthood. About 80 percent of eels on the market are raised using the latter timetable. An extreme shortage of eels is not expected for designated "doyo ushi" eel-eating days on July 20 and Aug. 1 this year. However, if the low fishing yield of shirasu unagi continues into April, then there will be a large impact on the eel market starting next year, and the Fisheries Agency explained that they will be keeping a close eye on the situation.

Q: So will everything be OK if there is a good catch in April?

A: Not so fast. The domestic yield for shirasu unagi was roughly 200 tons around 1960, but that number has continued to decrease since the 1970s, with a record low of some 5 tons caught in 2013. Following that, fisheries have been able to maintain roughly 15 tons per year, but that doesn't even account for 10 percent of the yield during the height of the industry. Every year, an increase or decrease in yield from the previous year becomes a hot topic, but just because there was a good catch in a particular year doesn't necessarily mean that the population of eels has increased overall.

Q: Isn't there a way to increase the number of shirasu unagi?

A: To prevent against overfishing, the government is regulating the amount of shirasu unagi caught in order to try to actively curb the population decrease. On the other hand, one of the biggest issues is also the worsening environmental conditions in rivers, which has led to a dwindling number of adult eels to even parent the juveniles. (Answers by Ryo Watanabe, Science & Environment News Department)

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