Why we don’t know if Irukandji jellyfish are moving south

Kylie Pitt
Swellnet Dispatch

Reports that Irukandji jellyfish might be moving south may be panicking people unnecessarily. It’s almost impossible to tell where the tiny jellyfish are along our coast, but that could change with new technology that can “sweep” the ocean for traces of DNA.

Since the Christmas period nearly twice the usual number of people have suffered the excruciating consequences of being stung by Irukandji. The stings are rarely fatal, but can require medical evacuation and hospitalisation.

The irukandji jellyfish, up close. Photo: Lisa Ann Gershwin/AAP

These reports of southward movement are almost a yearly tradition, often sensational, and accompanied by varying expert opinions about whether climate change is driving these dangerous tropical animals south, towards the lucrative beach tourism destinations of southeast Queensland.

But simply counting the number of Irukandji found, or the number of reported stings, tells us very little about where the species can be found.

A simple question but difficult answer

“Where are Irukandji located, and is that changing?”, might seem like a straightforward question. Unfortunately, finding the answer is not easy. The only definitive way to determine where they are is to catch them – but that poses many challenges.

Irukandji are tiny (most are about 1cm in diameter) and transparent. Along beaches they are usually sampled by a person wading through shallow water towing a fine net. This is often done by lifeguards at beaches in northern Queensland to help manage risk.

Irukandji are also attracted to light, so further offshore they can be concentrated by deploying lights over the sides of boats and then scooped up in nets. The problem is they’re are often very sparsely scattered, even in places we know they regularly occur, such as Queensland’s north. As with any rare species, catching them can confirm their presence, but failure to catch them does not guarantee their absence. Collecting Irukandji in an ocean environment is truly like searching for the proverbial needle in a haystack.

A sense of scale: an Irukandji Jellyfish next to a two dollar coin. Photo: WA Department of Parks and Wildlife/AAP

Another method is to infer their presence from hospital records and media reports of Irukandji syndrome, the suite of symptoms caused by their sting, but this method has major pitfalls. There is often a delay of around 30 minutes between the initial sting, which is usually mild, and the onset of Irukandji syndrome. Hence the animal that caused the symptoms is almost never caught and we cannot verify the species responsible.

Indeed, we do not know whether Irukandji are the only marine organisms to cause Irukandji syndrome. For example, the Moreton Bay Fire Jelly, a species of jellyfish related to Irukandji only found in southeast Queensland, and even bluebottles, which in the past couple of weeks have stung more than 10,000 people along Australia’s east coast, have also been suggested to occasionally cause Irukandji-like symptoms.

eDNA to save the day

Emerging technology may be the key to properly mapping Irukandji distribution. All animals shed DNA in large quantities into their environment (for example, skin cells and hair by humans). This DNA is called environmental DNA) (or eDNA) and genetic techniques are now so powerful that they can detect even trace amounts.

In the sea, this means we can determine whether an animal has been in an area by collecting water samples and testing them for the presence of the target species’ DNA. This technology is exciting because it provides a major upgrade in our ability to detect rare species. Moreover, it is relatively simple to train people to collect and process water samples, the results can be available within hours, and the equipment needed to analyse the samples is becoming increasingly affordable.

This means an eDNA monitoring program could be easily established in Southeast Queensland to monitor the occurrence and, importantly, changes in the distribution of Irukandji jellyfish. This is because Irukandji leave traces of their genetic code in the water as they swim.

Developing the eDNA technology for use with Irukandji would cost a few hundred thousand dollars – a relatively small price to pay to improve public safety, to provide stakeholders with some control over their ability to detect Irukandji, and to create some certainty around the long-term distribution of these animals.

//Kylie Pitt - Professor, Griffith University and Dean Jerry - Associate Professor of Marine Biology and Aquaculture, James Cook University

The authors would like to acknowledge the significant contribution to this article by Professor Mike Kingsford (James Cook University).

This article first appeared in The Conversation


hellomoon's picture
hellomoon's picture
hellomoon commented Wednesday, 6 Feb 2019 at 12:22pm

I surfed peregian beach noosa one month ago and while sitting on my ski spotted an Irukandji jellyfish twice in my hourly session.( Yes,I know what Irukandji look like}. My local council gave me a number to call so I could pass on this information,I left two messages and had no returned response. SO,I can tell you they are here and we will definately see an increase in sightings and stings.


seen's picture
seen's picture
seen commented Wednesday, 6 Feb 2019 at 6:35pm

Yeah, but why would they want to find them? no financial incentive, its not like they are going to net for them on the surf coasts, and none of the pollies / developers would want the headline "Irukandji invade Gold Coast / Noosa". So masterful inactivity will the order of the day until it can no longer be denied. The only people who might be motivated enough to discover the critters would be local surfers looking to clear the lineup... actually, come to think of it, a couple a hundred thou sounds doable...

Giovanni's picture
Giovanni's picture
Giovanni commented Saturday, 9 Feb 2019 at 5:08pm

Because they're not moving North?

truebluebasher's picture
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truebluebasher commented Sunday, 10 Feb 2019 at 11:16pm

Marine science is no longer an open book.
We've seen Qld Govt halving Shark incidents to protect tourism.
Irukandji stings also end with [ BEACH CLOSED ]
Oz wide Whale Beachings/Sharks are no different. All recall WSL boycott of WA.

{The secret life of The Irukandji }
Credited to various Qld/WA Scientists / Medicos dedicated to victims.

Irukandji are born on North reefs but colonize south reefs on 22 year Sun Spot Cycle

They head South harbouring calm East facing beaches or West facing Island Shores.
The 1st northern crews seem to deposit larger population with less venturing south.
South crew rely more on west facing afternoon sun needing warmer shallow waters.
This also keeps their sensitive fishing tackle out of the rough surf lineup as a rule.

Rainfall & Humans play a role in Nutrient level outfalls increasing Algal Blooms.
Algal Blooms attract the Salps / Sea Lice / Larval Fish closer to shore.
[ Tip ] Said mid summer critters on N/W Island of N/E Beach are a warning sign.
Irukandji are harbouring offshore waiting for the perfect time to feed.

Irukandji needs Wind to sail on the High Tide in full Sun in warmest waters.
Fraser Island waters (Nov- [Xmas/NYE]-Easter) (North Qld / Sept-May)

Wind as their sail.
High Tide releases pray from shoreline
Sun powers up their Reflective pearl like Fishing lures (Tentacles)
East facing am high tide N/E wind (or) West facing pm high tide N/W wind.

[WARNING] Do not enter said waters at these times. Irukandji has 2m fishing span .
Please refer to local waters treatment guidelines as 10+ species exist.
Hospitals now run Magnesium Sulphate Transfusions...(Pain / Hypertension)
Please note WA has larger population.Alternate winds/Beaches but apply same tides!

(Unusual traits)
Irukandji seldom waste energy coming ashore on wet/Dark/Cloudy days.
They power down their death rays at night.
Young Irukandji are either devoid of venom of have very little.

Notes: It seems Irukandji venom stems from diet (perhaps sea lice) + Age + Sun.
Mature species on hottest day will give biggest bang for your buck. (Real live wire!)
My theory may settle arguments over which town has most venomous...(None!)
All down to Diet / Maturity / Sun + Water Temperature < > charge up time!

Please forgive me! This last paragraph is just here say. (Based on fact but not proven)

End of season is a bit sketchy but it seems they regroup South & out to sea onto Reef.
(Again! Irukandji hideout is Marine Biology Holy Grail) Top secret!

Consensus is that EDNA phase one is only meant to supplement...not as lone tool.
As such requires double research funding to run alongside visual /Trad surveys.
The benefit in detecting new waters for Irukandji is down to contamination control.
Also note that EDNA can't differentiate how many as say algal dyes could track.
EDNA will no doubt benefit Marine Science but also opens the door for major error.

Spuddups's picture
Spuddups's picture
Spuddups commented Monday, 11 Feb 2019 at 6:43pm

Those Jellyfish sound pretty dangerous. Imagine if they ended up in force on the Gold Coast. Farken carnage. The whole tourism industry'd be right royally stuffed.