A 97% decline in giant cuttlefish population in South Australia's Spencer Gulf has been reported by the state government, with only 1,811 individuals counted this year compared to 63,000 last year. The count is the lowest since 2013, and marine biologists are attributing the decline to a harmful algal bloom that may have impacted the eggs and juveniles of the species. The number of eggs found along an 8-kilometer coastline was significantly lower than expected, with only 440 eggs recorded. There are calls for the giant cuttlefish to be listed as an endangered species, including from marine biologists and researchers who are urging the government to take action to protect the population.
Written by the local model on 2026-08-21,
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Story summary
A 97% decline in the population of giant cuttlefish in South Australia's Spencer Gulf waters has been recorded, with just 1,811 individuals counted this year compared to 63,000 last year. This is the lowest count since 2013, when there were only 13,000 cuttlefish. Marine biologists attribute the decline to an algal bloom, which may have impacted the population's ability to breed. In fact, researchers found a remarkably low number of eggs left behind in the area: just 440 along an 8-kilometer stretch of coastline. This has prompted calls for the giant cuttlefish to be listed as an endangered species. The South Australian Department of Primary Industries and Regions (PIRSA) conducted the count, which is part of a larger effort to monitor the health of the marine ecosystem in the Spencer Gulf.
Written for “Australian Cuttlefish Decline” on 2026-08-31,
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In short:
The South Australian government has released this year's giant cuttlefish count from the Spencer Gulf.
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The count shows an almost 100 per cent decline from the 63,000 cuttlefish counted last year.
What's next?
There are calls for the giant cuttlefish to be listed as an endangered species.
South Australia's Department of Primary Industries and Regions (PIRSA) says giant cuttlefish numbers are down by 97 per cent.
Last year the department counted 63,000 cuttlefish in the Spencer Gulf waters.
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department → show → waters
This year 1,811 were recorded.
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1,811 → record → ?
South Australian Research and Development Institute executive director Professor Mike Steer said the decline was being monitored closely.
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decline → say → ?
"The [giant cuttlefish] population has depleted and has likely been impacted by the algal bloom," he said.
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he → deplete → bloom
The number is the lowest since 2013, when Pirsa recorded 13,000.
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Pirsa → record → 13,000
Marine biologists visited the Spencer Gulf last month to count the eggs left behind.
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biologists → visit → eggs
"Along that 8 kilometres of coastline we only found 440 eggs," Manny Katz said.
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Katz → find → eggs
The annual gathering near Whyalla is one of the only known mass-breeding aggregations of its kind.
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gathering → know → kind
"It's the only place where our giant cuttlefish come for breeding," SA Climate, Environment and Water Minister Emily Bourke said.
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Bourke → come → breeding
"So we see this population as a priority to protect."
The future of the giant cuttlefish
Adult giant cuttlefish die shortly after spawning, leaving the next generation reliant on that single winter event.
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cuttlefish → see → event
"Normally when there's tens of thousands of cuttlefish and each female is laying dozens of eggs, you would expect there to be millions along the coastline," Mr Katz said.
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Katz → be → coastline
"My team went out and jammed our heads under every single rock we could at eight sites.
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we → go → sites
At some we found no eggs at all.
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It's probably an indicator that next year's population is going to be incredibly low as well."
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population → go → ?
Professor Steer said the one-two year life cycle of the species gave cause for hope.
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cycle → say → hope
"In 2013 when numbers dropped down they popped back up in a couple of years," he said.
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he → drop → years
"Cuttlefish breed one year, die, and then the resulting hatchlings make up the population next year."
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hatchlings → breed → population
Professor Steer said the harmful algal bloom was a likely cause of the decline.
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bloom → say → decline
"We saw those [giant cuttlefish] eggs successfully hatch last year," he said.
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he → see → ?
"Those went into the water where the bloom was present, where we'd expect to see those juveniles and sub-adults.
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we → go → juveniles
So it's likely that it's had an impact.
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"We did see a lot of fish perish as a result of the algal bloom.
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lot → see → bloom
We need to research into the food web structure."
Mr Katz is urging the government to protect the giant cuttlefish with a formal endangered listing.
"
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Katz → need → listing
They should be listed as an endangered species," he said.
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he → list → species
Invertebrates Australia has made an application for the species to be listed on the International Union for Conservation of Nature Red List of Threatened Species.
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species → make → Species
"I think now there's reason to warrant them being federally listed in Australia as an endangered species, to trigger more funding and monitoring for the future," Mr Katz said.
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Katz → think → future
A spokesperson for the federal government said in a statement that "the reduction in giant Australian cuttlefish populations in the Spencer Gulf is very concerning".
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reduction → say → Gulf
The spokesperson said Environment and Water Minister Murray Watt has asked that the Threatened Species Scientific Committee "urgently consider whether a listing for the Upper Spencer Gulf population of giant cuttlefish under the EPBC Act is appropriate, and if so, to undertake that assessment".
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listing → say → assessment
A joint research project between the state government and Adelaide University will track the Spencer Gulf giant cuttle fish population until 2028.
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project → track → 2028
Research is also being conducted on how cuttlefish numbers are calculated.
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numbers → conduct → ?
That will be funded with part of the federal and state governments' $165 million algal bloom response fund.
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