Blue-ringed octopus numbers, jellyfish stings spike on Adelaide beaches
Surf lifesavers have reported a higher-than-normal number of deadly blue-ringed octopus and jellyfish stings on Adelaide’s metropolitan beaches.
“We’ve been told it’s because of the warmer weather and the fact we haven’t had much movement of the water,” Surf Life Saving SA’s Sonya Williamson told ABC Radio Adelaide.
“We’ve had 273 reported jellyfish stings this summer … we haven’t had any reports of any blue-ringed octopus bites so far, which is a good sign.”
A member of the public contacted ABC Radio Adelaide to say they had found 17 octopuses at Somerton Beach two weeks ago.
Museums Victoria marine invertebrates senior curator Julian Finn, who regularly dives in South Australian waters, said the high number was not unusual.
“At this time of year, I have had no problem finding up to 30 blue-ringed octopuses on one dive, so they are quite common,” he said.
“There’s huge numbers of them out there.”
Octopuses moving about because of heat
The SA species is nocturnal. At this time of year its body is about the size of a five-cent piece and it spends most of its time hiding.
Dr Finn said blue-ringed octopuses generally hatched in November as part of their yearly cycle.
“Following hatching, they don’t settle in one spot,” he said.
“They tend to grow and move around until April, when mating commences and females settle down to lay their eggs.
“Males tend to die by about June and the females brood their eggs until November.”
However, he said the hot weather could mean octopuses were finding it “uncomfortable where they are” and were moving about, increasing the likelihood of being seen.
“I have no records saying there’s more out there, but maybe the combination of the time of year and the conditions and lots of people being at the beach means that we’re getting more reports,” Dr Finn said.
Pretty species with a deadly bite
Blue-ringed octopuses bite with a fast-acting toxin, and caused two deaths in Australia in the 1950s and 1960s.
But they are not aggressive and tend to retreat, and only bite if provoked.
Their toxin causes paralysis to a person’s voluntary muscles, and death usually occurs because of a lack of oxygen, meaning mouth-to-mouth resuscitation of a victim aids their recovery significantly.
Ms Williamson said their bite was usually fairly painless, but numbness could occur within a few minutes.
“Weakness and difficulty breathing is quite rapid,” she said.
“We suggest people, if they’re not swimming between surf life saving patrol flags, that they call triple zero.
“If possible, use a compression bandage and immobilise the patient, and if necessary, commence CPR and continue to do so until help arrives.”
The most common jellyfish in Adelaide’s waters is the non-tropical jimble — small, transparent and hard to see.
Its bite is not fatal but can be painful, and is best treated by soaking the affected area with hot water after any remaining tentacles have been picked off.