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Blue-lined octopus

Hapalochlaena fasciata

  • Cephalopods
  • IUCN: Least concern
  • Usual depth3–49 m
  • Water temperature19–29 °C
  • Best monthsJanuary, March, and April
  • How commonRare
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Photo credit: (c) Patrick Connolly, some rights reserved (CC BY) · CC BY · iNaturalist

About this species

The blue-lined octopus is one of four species of extremely venomous blue-ringed octopuses. It can be found in Pacific Ocean waters that stretch from Australia to Japan. It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern Queensland and southern New South Wales. It is relatively small, with a mantle up to 45 millimetres (1.8 in) in length. In its relaxed state, it is a mottled yellow-brown with dark blue or black streaks covering the whole body apart from the underside of its arms, but its vibrant blue markings appear as a warning to predators when it feels threatened. Along with its other closely related species, the blue-lined octopus is regarded as one of the most dangerous animals in the sea, and its venom can be fatal to humans. This benthic octopus is one of four members of the genus Hapalochlaena, with the other species being the greater blue-ringed octopus, southern blue-ringed octopus, and the blue-ringed octopus. The blue-lined octopus is the only species of the four to display lined iridescent blue marking, as opposed to circular iridescent blue marking that the three other species tend to exhibit.

Text from the Wikipedia article “Blue-lined octopus”, licensed CC BY-SA 4.0. Read the article

Where and when

Where it has been recorded

Worldwide

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Best months

Worldwide (open data)

  • January: 53 records
  • February: 39 records
  • March: 72 records
  • April: 70 records
  • May: 47 records
  • June: 31 records
  • July: 21 records
  • August: 23 records
  • September: 39 records
  • October: 12 records
  • November: 30 records
  • December: 24 records

Depth and water temperature

Depth

Mostly recorded at 3–49 m · Deepest record: 48.5 m

  • 0–10 m: 1 records
  • 10–20 m: 0 records
  • 20–30 m: 2 records
  • 30–40 m: 0 records
  • 40–50 m: 1 records

Water temperature

Recorded in surface water of 19–29 °C

  • 18–20 °C: 8 records
  • 20–22 °C: 62 records
  • 22–24 °C: 20 records
  • 24–26 °C: 0 records
  • 26–28 °C: 0 records
  • 28–30 °C: 2 records

Names and classification

English
Blue-lined octopus, blue-lined octopus
Names in 5 more languages
German
Blaugestreifter Krake
Spanish
Pulpo de líneas azules
Japanese
ヒョウモンダコ, (誤)ヒョウモンダコ
Korean
파란선문어
Simplified Chinese
藍紋章魚

Other scientific names: Octopus fasciatus, Octopus robustus

Similar species

Sources and credits

Names and taxonomy: WoRMS (CC BY 4.0) and the GBIF Backbone (CC BY 4.0). Photos: iNaturalist observers, each under the licence shown (CC0, CC BY or CC BY-SA).

  • Depth, temperature, months and maps: records from OBIS and GBIF under CC0 or CC BY.
  • Descriptions: Wikipedia, licensed CC BY-SA, each linked to its article.
  • Conservation status as published by GBIF (IUCN Red List).
  • 165 open-data records from 1886 to 2016.
  • Species data updated November 3, 2026.

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