Australia is home to the only mass cuttlefish gathering in the world. This year these giants didn't return

Every winter, more than 100,000 giant Australian cuttlefish congregate along the rocky coastline of Point Lowly in South Australia to mate. This occurrence is the only cuttlefish gathering in the world, and it draws thousands of enthusiasts each year. However, this year the cuttlefish did not return, marking a significant decline.

In a typical year, these large cephalopods put on colorful displays to attract mates, with the aggregation site stretching 8 kilometers along a shallow reef. The adult cuttlefish die after mating, so the next generation relies on the mating success of the previous year. This unique population is genetically distinct and is protected as a National Heritage-listed site.

The South Australian government reported record low cuttlefish numbers during May and June, with fewer than 10 seen per dive. While the exact cause remains unknown, hypotheses include a South Australian algal bloom, reduced food supply, and water temperature effects. The algal bloom, dominated by the microalgal species Karenia cristata, could have directly impacted the cuttlefish or reduced their prey.

The unusually warm winter water temperatures also pose a potential factor. Despite a 90-day tourism ban imposed by the state government, which provided a favorable environment for the remaining cuttlefish, more research is needed to understand the population's status and ensure its protection for future generations.