As of today, peak season now, through ~June 30. Earth Exhibit tracks the live conditions and flags it the moment it is on.
Each spring and early summer, Baltic herring (Clupea harengus membras) aggregate inshore in the Airisto inlet and nearby Archipelago Sea shorelines to deposit adhesive eggs on submerged vegetation and hard bottoms.
The event is spread over weeks, with multiple spawning waves; timing is governed by local water temperature and can vary year to year.
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 |
|---|
| Seili (Själö) visitor pier |
| Airisto Marina / Airisto Spa boat launch (Parainen / Naantali) |
| + 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.