Scientists develop early warning tool to predict blue fly outbreaks

Scientists develop early warning tool to predict blue fly outbreaks


The stinging cells leave a red line where the tentacle touched your skin and may appear beaded with spots along the affected area.

New South Wales beaches were swamped by a ‘bloom’ of blue flies swept by northeast winds in 2021, causing the bites of large numbers of bathers.

Dozens of blueflies also washed up on Australian beaches earlier this year in “mind-blowing abundance”, ABC News reported.

But research co-authored by Lawes and Schaeffer found that northeast and southeast winds were most likely to bring blueflies to beaches in Sydney’s eastern suburbs.

“Northeast is the most favorable wind condition for Bluebottle groundings at Coogee and Maroubra, while it’s mostly south and southeast for Clovelly,” Lawes said.

However, the proximity of blowflies to shore as well as ocean currents, waves, and temperature also play a role in the number of blowflies invading a beach.

Bluebottle First Aid

  • Do not let the sting area rub.
  • Blue tentacles may remain after a bite and are characteristic of blueflies. Carefully remove any adhering tentacles (remember that they can still sting you if all the nematocysts have not discharged).
  • Rinse the area well with seawater first, not fresh water, to remove any lingering stinging cells.
  • Place the affected sting area in warm water – no hotter than the rescuer can comfortably tolerate for 20 minutes.
  • If the pain is not relieved by heat or hot water is not available, apply cold compresses or ice in a dry plastic bag.
  • Send for medical help if symptoms persist or an allergic reaction occurs.

– Surf Life Saving Australia


“We know blueflies are not bothered by Sydney’s cold winter ocean temperature – up to 15 degrees Celsius – but are much more common from October to April,” Lawes said.

The same wind direction can also push blueflies to different ends of the range depending on whether they are left-handed or right-handed “meaning their floaters sit to the left or right of their tentacle body,” Lawes said.

However, scientists still do not know the lifespan of a blue fly or the influence of its behavior on its movements.

Ambulances are only called for about 1% of reported bites, Lawes said. “Although not fatal, bluefly bites can cause extremely painful stings which, although rarely, can induce anaphylactic and systemic physiological responses – which can cause serious harm, endanger the patient and put several hours to calm down.”

Although rare, Lawes said an intense reaction can lead to cramping or tight muscles that make it difficult to swim back.

Matthew Moore was swimming at Coogee Beach when he felt an unmistakable throbbing pain on his arm. He stopped to find himself surrounded by an armada of blueflies.

“There were dozens around me, so I stood still,” he said. “But even the slightest movement of your hands or legs would just pull those tentacles out, giving you an intense, searing sting.”

Moore was unable to swim to shore, but was pulled out of the water by a lifeline “by then I had been stung about eight times”.

Meeting Moore left her with blisters around her arms, neck and chest that lasted for several days.


“I wasn’t in great shape,” he said. “I came home and collapsed and slept for about four hours.”

Lisa-Ann Gershwin, director of the Australian Marine Stinger Advisory Service, said she couldn’t imagine swimmers putting on blue fly protective swimwear: “It’s just one of those things you grab on your chin , like flies in the backcountry or mozzies after the rain.”

But swimmers might need to wear stinger suits in the ocean to protect against other marine villains such as the Morbakka jellyfish, which Gershwin says can be deadly but currently appears to be rare. “If Morbakka becomes more common or more venomous, I think that would be prudent.”

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