The One and Only Mystery Circle – Found Only in Amami
The mysterious underwater circles found in the sand around Amami have intrigued locals since the mid-1990s. Although fishermen were aware of them for years, no one knew who—or what—was making them. Some even believed they were linked to ancient curses.
Then in 2012, a Japanese TV crew uncovered the truth: the circles are actually nests built by a newly discovered species of pufferfish, now known as the Amami Hoshizora Pufferfish. The species was later named one of the Top 10 New Species in the World by the International Institute for Species Exploration.
In 2020, a research team from the University of Western Australia found similar circular patterns at 100 meters deep using unmanned submersibles—but they were unable to spot any fish, making the Amami discovery even more remarkable.
🐡 A Natural Wonder Found Nowhere Else on Earth
Today, Amami Oshima remains the only place in the world where these pufferfish and their intricate sand circles can be observed in the wild. Over the years, scientists have begun to understand how and when the fish create them.
Tied to the lunar cycle, male pufferfish begin building their nests around every two weeks, especially near:
The Tōkan'ya no tsuki (10th day moon)
The Ariake no tsuki (25th day moon)
Each circle takes several days to complete. Males clear debris, dig patterns, and carefully arrange shells, creating a perfectly symmetrical, mesmerizing circle. The more beautiful the nest, the more likely it is to attract multiple females to lay their eggs.
📅 Predicted Nesting Dates for 2026
These are the estimated dates when new mystery circles will begin to appear in 2026:
April 27
May 12
May 26
From these dates:
Days 1–3: Males are actively building their nests
Days 3–4: Females arrive to spawn—your best chance to see the completed circle
Following days: Males guard the eggs, and the circle slowly fades with time
