After a worrying season in Whyalla, scientists are searching for answers over record-low cuttlefish numbers
For a few spectacular weeks each year, thousands of Giant Australian Cuttlefish gather in the shallow waters near Whyalla for one of the world’s great natural events.
But this year, the numbers are a bit of a worry.
Just 1,811 Giant Australian Cuttlefish were estimated during annual surveys in the Upper Spencer Gulf, the lowest number recorded since monitoring began in 1998.
This year’s poor season has already been felt in Whyalla, where cuttlefish tours were disrupted and the annual Cuttlefest celebrations only continued with land-based activities.
A 90-day exclusion zone was also introduced across the breeding site from July 1, keeping swimmers, snorkellers, divers and anchored vessels out of the area to give the remaining cuttlefish, their eggs and hatchlings some space.
Now scientists are trying to understand what has driven the dramatic decline, and what role the harmful algal bloom may have played.
A Tough Year For An SA Favourite
The annual gathering at Point Lowly, near Whyalla, is the only known mass aggregation of Giant Australian Cuttlefish of its kind in the entire world.
Every winter, the rocky coastline becomes a breeding ground, with the cuttlefish putting on the incredible colour-changing displays that draw hundreds of keen onlookers to the region.
Numbers are known to rise and fall dramatically, with previous estimates ranging from 13,500 in 2013 to 247,000 in 2020.
SARDI Executive Director Professor Mike Steer, who’s studied Giant Australian Cuttlefish for a large part of his career, said the population had shown it was capable of recovering from low numbers.
“As someone who has studied Giant Australian Cuttlefish for much of my career, it is disheartening to see numbers this low. While this is the lowest population estimate we have recorded, we know from the past that this population has the capacity to recover when conditions are favourable,” Professor Steer said.
“In 2013, the population was estimated at a previous low of 13,500 animals, but within two years it had increased to around 100,000. That history shows how quickly the population can increase under favourable conditions.”
He said it was also encouraging to see adults continuing to return to the aggregation area, with spawning occurring and eggs being laid.
Scientists Look For Answers
A new joint research project between the State Government and University of Adelaide will look more closely at what drives changes in the population and what this year’s record-low numbers could mean for future breeding seasons.
Researchers will update population modelling and investigate the potential impact of the algal bloom, while collected cuttlebones will be analysed to learn more about breeding age and whether the population includes two distinct age groups.
The work will also help fisheries, tourism operators, Whyalla City Council and government agencies better understand the population’s vulnerability and plan for future seasons.
The research forms part of the Australian and South Australian governments’ $165 million algal bloom response and recovery measures.
For one of South Australia’s most incredible natural spectacles, 1,811 is a sobering number.
But with adults still spawning and eggs being laid, there are at least some positive signs beneath the water.
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