The octopus, which was captured for a research project, laid more than 5800 eggs in her tank at the Cronulla Fisheries Research Centre of Excellence.

Researcher Steve Montgomery said after the octopus spawned it turned itself inside-out like an umbrella and covered the eggs that were at the bottom of the tank.

The eggs then slowly hatched over a number of days.

"She will form a nest to protect those eggs until most are hatched and won't feed,'' Dr Montgomery said.

"We don't know for sure with this type of octopus, but ... we expect that once the eggs are finished hatching she will die.''

Dr Montgomery said the Cronulla research centre currently housed eight octopuses as part of a world-first research program into ageing and mortality.

"No one has studied Octopus Australis, but it is a large part of the prawn fishery and we need to know how how they live and how they die, to manage that resource.''

Dr Montgomery said some types of species had growth rings, similar to those on trees, that could be used to work out their age.

These translucent rings are deposited on a stylet at the base of the brain.

The scientists mark the animals with a chemical stain and then use that to try and work out how often the rings are made and hopefully, the age of the animal.

Once they know the animal's age, they use the information to set fishing quotas and work out populations.

According to Dr Montgomery, an octopus is a highly intelligent animal and these ones quickly worked out the scientists' habits.

"We lock them up carefully because they are major escape artists,'' he said.

"They change colour depending on background and, if cranky, they puff themselves up and go white with black rings around their eyes.''

He said one octopus would come to the surface at feeding time and squirt the scientists with water.

"There may be a personality problem with that octopus,'' he said.