Octopuses give up secrets

Peter Morse with a blue ring octopus. Picture: Andrew Ritchie d421378
Peter Morse with a blue ring octopus. Picture: Andrew Ritchie d421378

‘Essentially, it’s studying the population distribution and genetic structure of the southern blue ring octopus because it’s an animal we know virtually nothing about,’ Mr Morse (28), a third-year James Cook University doctorate student, said.

The traps placed under small black buoys near rock reefs caught none of the cephalopods at Dutch Inn, but others on the open seabed were successful because they may have offered some of the only shelter available for the animals.

Traps were also set off Rockingham, South Fremantle, Marmion and Hillarys, while about 110 animals caught in Cockburn Sound were found to be closely related.

The captures allowed Mr Morse to get genetic samples for blue ring octopus in areas between catches by recruited commercial fishermen that produced 90 per cent of about 200 animals used in his research between Albany and Dongara since January.

A genetic map of the species along all WA’s coast may show if there are sub-species, whether development such as dredging or marinas could interfere with mating and how newborn octopuses reach new coast, and if distinct groups exist.

‘In Albany, we were getting them in one bay where they were huge, about the size of your fist, whereas in another bay they were about 3cm at the largest,’ Mr Morse said.

It was possible blue ring octopuses’ short lives, currently thought to be seven months, could play a part in producing differences by allowing many generations over relatively short evolutionary time spans.

‘And they go out with a bang, with the males spending the last one to two months of their lives breeding furiously and the females guarding eggs, before they die a few weeks after the eggs hatch,’ Mr Morse said.

He will now analyse the genetic samples from the octopuses at the university’s laboratory in Queensland.

‘I suspect not many people see them in WA because they are nocturnal,’ Mr Morse said.