Octopus vulgaris grows to 25 cm in mantle length with arms up to 1 m long. O. vulgaris is caught by bottom trawls on a huge scale off the northwestern coast of Africa. More than 20,000 tones are harvested annually.
The common octopus hunts at dusk. Crabs, crayfish, and bivalve mollusks (two-shelled molluscs such as cockles) are preferred, although the octopus will eat almost anything it can catch. It is able to change colour to blend in with its surroundings, and is able to jump upon any unwary prey that strays across its path. The prey is paralyzed by a nerve poison, which the octopus secretes in its saliva, and the octopus is able to grasp its prey using its powerful arms with their two rows of suckers. If the victim is a shelled mollusc, the octopus uses its beak to punch a hole in the shell before sucking out the fleshy contents.
Octopus vulgaris has individuals of both sexes. During mating, the male approaches the female, who fends him off for a while, but then accepts him. He sits next to her or mounts her, inserting the hectocotylus in her mantle cavity to pass the spermatophores. They may copulate for several hours. The same pair often repeat mating over a period of a week or so. Females become restless and search for a sheltered place where they can lay and brood the eggs without disturbance. Eggs are laid in shallow water. They are always attached to a substrate. On rocky shores, females find a hole, a crevice or sheltered place and they often protect their homes with shells, stones and other solid objects that they gather. Coral reefs provide suitable shelter. On sandy or muddy bottom, eggs are laid in empty mollusc shells or in man-made objects such as cans, tins, bottles, tires, boots, and amphorae . In tropical and subtropical waters, eggs are laid throughout the year. The total number of eggs laid by a female varies from 100,000 to 500,000. During egg laying and subsequent brooding, the female rarely leaves the egg mass. She usually does not feed during the entire period of spawning and brooding, which can be as long as 4-5 months at low temperatures. Egg care includes cleaning the eggs with the arm tips and directing jets of water from the funnel through the strings. Intruders, including potential prey, are pushed away, although crabs left overnight may occasionally be eaten. As a rule, females die shortly after the hatching of the last embryos after losing one-third of their pre-spawning weight.
There is the potential for the overfishing of these animals, which threatens their proliferation. However, at this time, they are not at any specific risk.
These animals have a life span of 12 to 24 months.