Common Octopus

Photo: Susanne Spindler · CC BY-NC-ND

The artificial reef's complex matrix of concrete cavities creates ideal territory for octopus, which establish individual dens and defend them fiercely from competitors. Divers frequently spot the give-away pile of crab and bivalve shells outside occupied dens, allowing patient observers to watch feeding behaviour and colour-change communication. At night, octopus roam the reef surface and are far more active and visible than during daytime.