University of Auckland marine ecology professor Rochelle Constantine said the current El Nino weather pattern was changing the direction of the wind and meant jellyfish were being blown in from the open ocean.
Influxes of bluebottle jellyfish occur mostly along West Coast beaches due to the prevailing wind.
But warmer water temperatures and longer days during summer also mean the jellyfish population is growing larger due to an abundance of food.
That means more jellyfish being spotted on beaches: “It’s a summer treat for New Zealand.”
Constantine said it was important to note bluebottle jellyfish can still sting people a long time after they are dead.
The float of a bluebottle jellyfish does not sting - it is the long blue threads or attached tentacles.
“Those tentacles can be 1-2m long, so you may not even see the float of a bluebottle near you in the water - and you’re getting stung.”
Swimmers should be mindful that if there are lots of fresh bluebottles washed up on the beach, they may be close by in the water.
“Some people wear wetsuits and long rash shirts, but your hands, face and feet are still vulnerable.”
Bluebottle jellyfish survive on zooplankton and are colony animals - what we see as one bluebottle is actually a colony of little jellyfish under a single float.
The warmer water, long days and increased light means there are more phytoplankton and thus zooplankton for bluebottles to survive on. All of these things make attractive conditions for bluebottle jellyfish.
“I think this isn’t the end of it. They’ll probably continue for more of the summer.”
The tentacles of a bluebottle jellyfish can stretch up to 1-2m in the water. Photo / Bevan Conley
How to treat bluebottle jellyfish stings
The first important step is to immediately wash the tentacles off of your body, Constantine said.
“Flush it off with water or a hose, or even in the sea if there is a clear area. Just try to get them off you as soon as possible, or flick them off with a towel.”
Then run the area under lukewarm tap water. Afterwards, applying an ice pack can help to relieve pain.
Old solutions used to be applying vinegar or methylated spirits to the sting, but Constantine said this was no longer advised as it could irritate the area.
“It’s going to hurt, but that hurt will pass. In very rare occasions, people may be allergic to the sting.”
Babies and older people are more vulnerable to stings, and for strong reactions, medical attention is necessary.
Eva de Jong is a reporter for the Whanganui Chronicle covering health stories and general news. She began as a reporter in 2023.
