Japan is steeped in century-old rituals where people traditionally eat grilled freshwater eel on "doyo no ushi no hi," the day customarily dedicated to eating eel.

Eel day fell on July 22 this year, but concern over dwindling stocks in Japan is growing, with other countries in the region reporting a similar trend. Continued demand for juvenile eel has led to an increase in the smuggling of glass eel from Indonesia to Japan and China, prompting Jakarta to toughen regulations.

In Japan, eel is commonly eaten in the summer but is also the main ingredient in several year-round dishes. But making the dishes is getting more expensive, given that the annual eel catch has recently sunk to about 200 tons from around 3,000 tons in the 1960s, according to the Agriculture, Forestry and Fisheries Ministry.