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An amorous octopus has been released from Dunedin's Portobello Aquarium to sow his wild oats at sea.

The octopus, known as "Sid", who was a star attraction of the aquarium, was freed after trying to escape several times.

He was once caught heading for the door after hiding out in a drain, said Tessa Mills, manager at the New Zealand Marine Studies Centre yesterday.

He vanished from his tank late last year, and was missing for five days. He escaped again twice last month, using a drain to seawater tanks outside the aquarium.

"They can be very intelligent, and once they have worked out that there is an escape route, it is difficult to stop them," Ms Mills said.

An octopus could squeeze through any tiny gap larger than its eye, and could be as intelligent as a puppy.

It was likely he was driven by a strong mating instinct, she said.

Aquarium spokesman Peter Bell said: "We expect him to be enjoying life immensely swimming around the harbour and meeting up for a few liaisons with some female octopus out there." He said Sid's "hard and fast" lifestyle would unfortunately come to an end after mating.

"He'll probably swim around for a number of weeks and have a number or partners in that time.

"They tend to die following mating, or in the female's case after they've laid their eggs and they have hatched."