Golden Flangetails signal river recovery across Tokyo

July 13, 2026Taiheiyo evergreen forests

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(Sinictinogomphus clavatus) have appeared six times across Tokyo since late May — their southernmost record reaching a reclaimed park at the bay edge in Ota on June 24. These dragonflies are exacting about water quality: their nymphs develop in clean gravel-bottomed streams, making their presence a reliable indicator of gradual river recovery and improving substrate conditions.

The broader damselfly and dragonfly fauna is active this season, with 81 odonatan records logged over the past month as calm summer conditions stratify the water column. It's a fitting abundance for a place whose ancient Japanese name, Akitsushima, means "island of the dragonflies" — a heritage that still rings true in the current ecology.

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