The president of a suburban lifesaving club says jellyfish numbers in Port Phillip Bay are the worst he has seen in 20 years.
The translucent red lion's mane jellyfish have been sighted at beaches all around Melbourne, from Altona to Edithvale.
Brighton Life Saving Club's Sam Dimopoulos said the creatures have put many people off swimming at Brighton beach.
"The jellyfish this year have been unbelievable," he said.
"We've got guys who don't miss their swims — they are not going in the water at the moment.
Of the people who have been brave enough to get in the water, Mr Dimopoulos said some have been stung.
"I've felt them, it's not fun," he said.
"I recommend swimming in groups, if you are swimming alone and you find yourself in a pool of these jellyfish it can be quite scary."
Summer rain fuelling swarms
Port Phillip Baykeeper Neil Blake said the particularly large jellyfish blooms this summer could be due to the La Niña weather system.
"The extra rainfall … is flushing a lot more nutrients into the bay and therefore providing the source of life, really firing up the food chain," he told ABC Radio Melbourne's drive program.
Aquarist for SEA LIFE Melbourne Aquarium Pat Noble said plentiful food combined with warm weather created ideal conditions for jellyfish to reproduce.
"As the water temperature starts to get above 18 degrees jellyfish polyps begin to strobilate, which produces juvenile jellyfish known as ephyra," he said.
"The ephyra grow into adult jellyfish, which we commonly see blooming over summer."
While the lion's mane jellyfish (Cyanea annaskala) commonly found in Port Phillip Bay can sting, Mr Blake says for most people it is mild.
"There is a concern that some individual people may have an allergic reaction and therefore will need to get immediate medical attention," he said.
What to do if you get stung
If someone gets stung by a non-tropical jellyfish like the lion's mane, St John Ambulance training team leader Alison Osborne suggests the following:
- Do not rub the stung area
- Remove any remaining tentacles (try not to use your bare hands)
- Rinse the area with seawater to remove any invisible sting cells (do not use fresh water — this can set off additional stinging cells and cause more pain)
- Put the stung area in hot water for 20 minutes (hot water will help to deactivate the jelly fish toxins and reduce pain)
- If the pain does not ease from the application of hot water, or if you do not have access to hot water, apply a cold pack
If the pain is ongoing or you are unsure what you were stung by, Ms Osborne says it is best to seek further medical advice.
