419 Dive Log Australasia AUGUST 2026

One of the most fascinating things about the Southern Blue-ringed Octopus is the way the female broods her eggs. Unlike many octopuses that attach eggs to the roof or wall of a den, female Southern Blue-ringed Octopuses carry their eggs under the body, held in the arms and webbing. This means the clutch is mobile. The female is not fixed to one place in the same way as a den brooding octopus. It is reasonable to suggest that a brooding female can move with her eggs because she physically carries them. I photographed one egg-carrying female in a particular spot, and she was gone the following day. While I will never know exactly why she moved, I believe it suggests that if a brooding female feels her location has been compromised or is no longer safe and secure, she may relocate with her clutch because the eggs are carried with her. That said, it would be too strong to claim that a female moves simply because a careful diver or photographer has spotted her. The young of the Southern Blue-ringed Octopus do not spend their early life drifting as plankton in the open water. Instead, they hatch as tiny, fully formed

octopuses, ready to live on the seafloor. This is important. Many marine animals disperse widely as larvae, carried by currents before settling somewhere else. The Southern Blue-ringed Octopus has a more localised start. Its young hatch into the same general benthic world as the adults. The famous blue rings, however, are not immediately obvious in the hatchlings. They become more visible as the young develop. Port Phillip Bay is excellent octopus country, and the Southern Blue-ringed Octopus is only one part of that story. The bay supports a surprisingly diverse mix of octopus species. The ones divers are most likely to encounter are the Southern Keeled Octopus (Octopus berrima), M ā ori Octopus (Macroctopus maorum), Pale Octopus (Octopus pallidus) and Southern Sand Octopus (Octopus kaurna). Less commonly encountered species include the Southern White-spot Octopus (Callistoctopus bunurong) and Frilled Pygmy Octopus (Octopus superciliosus), along with occasional reports of the Double-spot Octopus (Callistoctopus sp. 1).

This curious individual came so close it almost climbed onto my camera.

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Dive Log Australasia #413 August‘29

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