Recently Yomiuri News reported the following:
On 14th, a court in Tokushima handed down sentence to the director of Greenwood Freshwater and one employee for selling split and broiled eels from China and Taiwan but falsely claimed that they were from Tokushima. The judge, having considered 'the long period of cheating, and the admitting of the charge', sentenced both to two-year imprisonment. The court verdict showed that during the period from June 2006 to February 2008 the two defendants, in collaboration with the director of a food company who had been found guilty separately, sold 39 tons of eels from China and Taiwan, but falsely claimed that they were from Tokushima. Also, in 2008 from March to December they collaborated with another former food company director, now a defendant of another court case (court judgment pending), put China and Taiwan split and broiled eels into corrugated paper boxes and labeled them as product of Tokushima. About 3 tons of eels were sold to retailers in various locations.
So next time when you see eels in markets in Japan, don't be so sure that they must be a product of Japan, even if they are labeled as such.