Bluebottle-fish Australia – Nomeus gronovii Facts & Sighting

Bluebottle-fish, Nomeus gronovii. [Manly Wharf, Sydney, 2025]

🐟 Meet the Bluebottle-fish (Nomeus gronovii)

Spotted a striking blue fish near a bluebottle jellyfish on the Australian coast? Chances are you've just crossed paths with the Bluebottle-fish (Nomeus gronovii), also known as the Man-o'-war Fish. One of the ocean's most daring little hitchhikers — the Bluebottle-fish lives life on the edge, quite literally.

This small pelagic fish is famous for one extraordinary survival trick: juveniles shelter among the stinging tentacles of the Portuguese Man-o'-War (Physalia) — using its deadly host as a shield against predators. Despite not being fully immune to the venom, they hold their ground, even feeding on the tentacles themselves.

Recognised by their vivid blue backs, silver sides with blue blotches, and large dark pelvic fins, juvenile Bluebottle-fish are most commonly seen along Australia's east and west coasts during summer, when Bluebottles wash inshore. They range from Fremantle (WA) to eastern Victoria and have been recorded around Lord Howe Island.

Growing up to 39 cm, this species is listed as Least Concern on the IUCN Red List — but an encounter with one is anything but ordinary.

Size: Up to 39 cm. | Conservation status: IUCN Least Concern.