As of today, out of season, returns ~September. Earth Exhibit tracks the live conditions and flags it the moment it is on.
Each autumn mature ayu (Plecoglossus altivelis) migrate downstream from upland rivers toward estuaries to spawn.
In Yamagata Prefecture the downstream run concentrates fish near river mouths and shallow estuarine channels for several weeks, creating predictable viewing opportunities for anglers and wildlife observers.
Where to see it
A taste of where to see it. The full map, exact coordinates and the best timing for each spot live in the app.
| Viewing spots |
|---|
| Mogami River Estuary at Sakata Port |
| Mogami River Bank near Shinjō (Shinjō Riverside Viewing) |
| + 1 more spot, with exact coordinates and timing, in the app → |
This is the short version
This page shows a taste. The app has the full list of where to see this, the exact timing, and live conditions for 1,000+ natural phenomena worldwide, so you know the moment one is genuinely worth the trip.