More monitoring and research for Giant Australian Cuttlefish as numbers reach historic lows

A joint research project between the state government and Adelaide University is developing a better understanding of the life history and drivers of population change in cuttlefish. It will include:

• Updating modelling to better estimate population size and variability, assess extinction risk — including potential algal bloom impacts — and guide long term management and conservation of the Cuttlefish Coast Sanctuary Zone.
• Collecting cuttlebones for Adelaide University to analyse breeding age and identify whether the population includes two distinct age groups.
• Improving understanding of the cuttlefish population's vulnerability to help fisheries, tourism operators, Whyalla City Council and government agencies plan for future seasons.

The project is funded through the Australian and South Australian Governments’ $165 million investment in algal bloom response and recovery measures.

Aggregation of cuttlefish at Point Lowly, near Whyalla, in Upper Spencer Gulf, is a globally unique natural phenomenon, and one of South Australia's most important marine wildlife and tourist attractions.

DEW the South Australian Research and Development Institute (SARDI) completed underwater surveys this month, and while annual cuttlefish numbers are known to fluctuate naturally, this year’s population estimate is 1,811 – the lowest on record.

Cuttlefish numbers naturally rise and fall from year to year since SARDI surveys began in 1998 and have previously ranged from 13,500 in 2013 to 247,000 in 2020. After concern for the low number in 2013, the population estimate rapidly increased to more than 100,000 by 2015. These boom-and-bust cycles are typically driven by environmental conditions, including temperature and food sources.

On July 1, the state government implemented a temporary restriction on recreational activities to better protect cuttlefish at their Upper Spencer Gulf breeding site.

The 90-day exclusion zone – which restricts in-water recreational activities, including swimming, snorkelling and diving, as well as vessel anchoring – aimed to minimise any disturbance on breeding cuttlefish, and help protect their eggs and hatchlings.

Impacted cuttlefish tour operators in the region are eligible to apply for the Algal Bloom Small Business Support Grants.

In 2022, regulations to prohibit the taking of cuttlefish in the northern Spencer Gulf were reinstated. The regulations were enshrined in law through The Fisheries Management (Cuttlefish–Northern Spencer Gulf) Amendment Bill 2025, formalising the regulations including a fine of up to $20,000 for anyone caught taking Great Australian Cuttlefish.

Quotes attributable to Executive Director at SARDI, Professor Mike Steer 

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.

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. 

It was also encouraging to see adults continuing to return to the aggregation area, with spawning occurring and eggs being laid. Those are positive signs that the breeding cycle is continuing and that the population retains the potential to build again over coming years.