KOCHI, Jan 27, 2026 (News On Japan) - From a hill overlooking the river mouth, countless boats could be seen floating below, their multicolored lights reflecting off the shimmering surface of the water, while the hum of engines and the voices of fishermen occasionally drifted through the night air.
The Shimanto River, which flows through western Kochi Prefecture, comes alive in winter with boats targeting glass eels, juvenile Japanese eels measuring about five centimeters in length. Fishermen use fish-attracting lights such as underwater LEDs and scoop the tiny eels with nets roughly 15 centimeters in diameter.
Japanese eels are believed to be born near the Mariana Islands before riding ocean currents such as the Kuroshio to reach the coasts of East Asia from winter to spring. Taking advantage of the species’ habit of migrating from the sea into rivers at night to grow, fishermen operate near river mouths. The activity is said to peak during spring tides around the new moon, when upstream migration intensifies, a period known locally as the “dark spring tide,” drawing even more boats onto the water when the tides begin to move.
“You have to wait perfectly still, so the cold really gets to you. Some people say it’s tough to even go out this year because the catch is so poor,” said Isao Matsuoka of Shimanto, who is well acquainted with the fishery. In contrast to last year’s abundant harvest, catches have been scarce this season, with some nights yielding only a few eels.
Glass eels are sold to aquaculture operators through distributors and can fetch prices exceeding 2 million yen per kilogram, earning them the nickname “white diamonds.” The high value has attracted many part-time fishermen to the river.
The lucrative trade has also led to repeated cases of poaching and illegal transactions. In Kochi Prefecture, limits on fishing seasons and catch volumes have been set to ensure proper resource management. From this fiscal year, new legal requirements mandate that glass eels be numbered and that transaction records be created and stored, as systems are put in place to improve transparency in distribution.
Calling the Shimanto River “a treasure trove,” local residents take pride in the waterway. While the environment surrounding this winter tradition on a rich river is gradually changing, it continues to support Japan’s deeply rooted eel culture. The lights shimmering on the water remain a beacon for the future.
Source: 産経ニュース
