Source: The Conversation (Au and NZ)
This year’s cuttlefish season has been unlike any other.
Every winter, more than 100,000 giant Australian cuttlefish can usually be found mating along the rocky coastline of Point Lowly, northeast of Whyalla, South Australia. They put on shapeshifting, colourful displays in their attempts to attract a mate.
This is the only cuttlefish aggregation in the world. In a typical year, thousands of enthusiastic fans travel to regional SA and brave the freezing water temperatures to experience this unique phenomenon.
In stark contrast, this year’s cuttlefish season has seen significantly fewer cuttlefish, and tourists have been kept away.
What makes this cuttlefish aggregation so unique?
Giant Australian cuttlefish are the world’s largest cuttlefish species, and are only found in southern Australia.
Cuttlefish are cephalopods, a type of advanced mollusc that also includes octopuses, squids and nautiluses.
Adult giant cuttlefish typically congregate in small groups to mate. But at Point Lowly, one special population forms a single, large mating aggregation along an 8 kilometre stretch of shallow reef. Like most cephalopods, the cuttlefish life cycle lasts about a year. In winter, eggs are laid at the aggregation site, which hatch in spring; juveniles then spend the summer and autumn months growing in deeper waters, before adults return to the aggregation site. Crucially, after mating, all adult cuttlefish die, meaning the next generation is dependent on the mating success of the previous year.
This population of giant Australian cuttlefish is genetically distinct from those found in the rest of the country. The aggregation is considered a rare natural phenomenon and is National Heritage listed.
wildestanimal/Getty
What happened to the cuttlefish in 2026?
During May and June, tourism operators at Point Lowly reported extremely low cuttlefish numbers, often seeing fewer than ten cuttlefish per dive in areas where one would typically see 100 or more.
In July, significantly reduced cuttlefish numbers were confirmed by the SA government, which regularly surveys the aggregation. While cuttlefish numbers fell to a record low in 2013, there were still thousands of animals – abundant compared with 2026.
What we’ve seen this year is unprecedented. While the timing of the cuttlefish aggregation can vary slightly each year, by late June the animals should be well and truly aggregating. In short, the cuttlefish have simply failed to turn up.
What could be causing this?
While we’ll never know for sure, we can work towards some hypotheses.
On the balance of probabilities, the decline is likely linked to the SA algal bloom in some way. We’re taking into account the extent and rapidity of the cuttlefish decline, relative to past years, and the unprecedented nature of the algal boom’s ecological impact.
The algal bloom was dominated by Karenia cristata microalgae species, which can have a significant and swift impact on cephalopod populations, as seen in Australia and other countries. Cuttlefish could have been directly exposed to the bloom, or it might have reduced their food supply. Cephalopods are obligate carnivores and hunters, meaning they must eat live food such as crabs and shellfish. A decline in prey could have significant impacts.
Another hypothesis is water temperature. It is generally thought winter water temperatures influence the timing and success of the breeding aggregation. However, winter water temperatures have been relatively warm in the past, while a decline in numbers at this scale has not been seen before.
Some aspects of giant cuttlefish biology are still a mystery, so there could be other reasons for the decline that remain unknown.
Can anything be done?
Cephalopods reproduce quickly and grow fast. As such, the giant cuttlefish could bounce back if conditions are good, food is abundant, and there aren’t too many hungry predators around. However, there are still many unknowns that may impede their recovery – more research is needed to understand this unique cuttlefish population.
On a positive note, a 90-day tourism ban imposed by state government gave the remaining cuttlefish the best possible chance to thrive. This move was supported by local tour operators and communities, despite its economic impacts.
Furthermore, Invertebrates Australia is convening a working group of researchers, experts and tourism operators to compile the best available evidence on the status of the giant Australian cuttlefish population at Point Lowly. This will contribute to a review of the population’s conservation status on the world-leading IUCN Red List.
There was media coverage of a “bubble curtain” that was installed to protect the cuttlefish during the algal bloom. It was designed to protect the vulnerable eggs, which are attached to rocks, from the bloom. However, the eggs hatched without issue, and so the bubble curtain was not required.
We’re lucky to have this unique wonder in Australia, and the more research we can do, the more we can do to help protect these animals for future generations to enjoy.
Zoe Doubleday receives funding from the Australian Research Council and Marine Bioproducts CRC, and has previously received funding from the Fisheries Research and Development Corporation.
Bethany Jackel receives funding from the Ecological Society of Australia, and previously from the Department for Environment and Water, as well as research assistance from cuttlefish tourism operators.
Original source: https://analysis1.mil-osi.com/2026/08/10/australia-is-home-to-the-only-mass-cuttlefish-gathering-in-the-world-this-year-these-giants-didnt-return/