22nd December 2025 – (Osaka) Osaka’s Dotonbori district, famed for its neon-lit billboards and the iconic Glico “running man” sign, has become the focus of an unexpected natural spectacle after an unusually large shoal of fish was seen crowding the surface of the Dotonbori Canal, drawing widespread attention across Japan.
According to Japanese media reports, the phenomenon was first observed on 18 December, when vast numbers of fish suddenly appeared in the canal, at times seeming to carpet almost the entire water surface. Footage broadcast by Yomiuri TV showed passers-by stopping along the riverbank, visibly astonished by the dense, shimmering mass in the water. Witnesses told reporters that the fish appeared suddenly at around 6am to 7am that morning.
Videos posted to social media platform X (formerly Twitter) showed the canal teeming with fish, packed so tightly that the water beneath was barely visible. One clip quickly went viral, attracting more than 80,000 likes and a flood of comments. Many users expressed concern that the behaviour might be linked to seismic activity, with some recalling that unexplained fish kills and unusual marine movements had previously been reported before major earthquakes in Japan. Comments included speculation that the sudden influx could be “a sign of a big quake” and references to similar anecdotes ahead of the 1995 Great Hanshin earthquake.
The episode also sparked surprise for another reason: Dotonbori Canal has long been associated with poor water quality, and several users remarked on how unexpectedly clear the water now appears, asking when the notorious waterway had become so transparent.
In response to mounting speculation, experts have moved to offer scientific explanations. (Shoko Matsui, a specialist at the Osaka Museum of Natural History, told local media that the fish were likely a school of small mullet that had followed tidal currents into the canal in search of food, although she cautioned that the precise trigger for such a mass gathering remains uncertain. Other experts noted that mullet are highly sensitive to temperature changes and may move rapidly when sea temperatures drop, seeking relatively warmer waters in inner canals such as Dotonbori.
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