Giant cuttlefish population down by 97pc, SA count shows

South Australia's iconic giant cuttlefish population has plummeted by an alarming 97 percent, according to the latest count by the Department of Primary Industries and Regions (PIRSA). Last year, researchers recorded 63,000 of the marine creatures in the Spencer Gulf waters. This year, that number has crashed to just 1,811.

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The [giant cuttlefish] population has depleted and has likely been impacted by the algal bloom.

This drastic decline has prompted urgent concern among scientists and conservationists. Marine biologists visiting the Spencer Gulf last month were shocked to find only 440 giant cuttlefish eggs along an 8-kilometer stretch of coastline. "Along that 8 kilometres of coastline we only found 440 eggs," said Manny Katz, owner of Whyalla Dive Shop and director of Eyre Lab. He added, "My team went out and jammed our heads under every single rock we could at eight sites. At some we found no eggs at all."

The annual gathering of giant cuttlefish in the Spencer Gulf near Whyalla is one of the world's only known mass-breeding aggregations of its kind. "It's the only place where our giant cuttlefish come for breeding," stated SA Climate, Environment and Water Minister Emily Bourke. "So we see this population as a priority to protect." The future of this unique breeding event is now in serious jeopardy.

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Along that 8 kilometres of coastline we only found 440 eggs.

While adult giant cuttlefish die shortly after spawning, the species typically shows resilience. "In 2013 when numbers dropped down they popped back up in a couple of years," explained Mike Steer, executive director of the South Australian Research and Development Institute. However, the current situation is dire. Steer believes a harmful algal bloom is the likely culprit. "We saw those [giant cuttlefish] eggs successfully hatch last year," he said. "Those went into the water where the bloom was present, where we'd expect to see those juveniles and sub-adults. So it's likely that it's had an impact."

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It's the only place where our giant cuttlefish come for breeding.

Conservation efforts are intensifying, with Invertebrates Australia applying for the species to be listed on the International Union for Conservation of Nature Red List. Katz is urging for federal endangered status in Australia. "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," he said. A spokesperson for the federal government acknowledged the situation is "very concerning" and that Environment and Water Minister Murray Watt has asked the Threatened Species Scientific Committee to urgently consider a listing under the EPBC Act. A joint research project between the state government and Adelaide University will monitor the population until 2028, funded by a $165 million algal bloom response fund.

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So we see this population as a priority to protect.