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Environment
Jun 23, 2026
Analyzed by GPT OSS 120B

Whyalla’s Cuttlefish Gathering Threatened by Historic Algal Bloom

AI Summary
Mid‑June, when thousands of giant Australian cuttlefish normally swarm the Spencer Gulf for breeding, only a few dozen have been seen. Scientists link the dramatic decline to the nation’s largest toxic algal bloom, raising concerns for the ecosystem and local tourism.

Unexpected Decline of the World‑Famous Cuttlefish Aggregation

Mid‑June is traditionally the peak of the giant Australian cuttlefish spawning event near Whyalla in South Australia’s Spencer Gulf. This year, instead of thousands, divers have recorded only a few dozen skittish individuals.

The Toxic Algal Bloom’s Direct Threat

Researchers attribute the shortfall to the ongoing bloom of Karenia cristata, the largest and most destructive algal event in Australian history. The bloom, first detected in March 2025, continues to coat coastal waters with toxic cells that are “swift and fatal” to cephalopods, according to marine ecologist Zoe Doubleday.

Testing Data Highlights Algal Intensity

  • Elevated levels detected at 8 of 32 monitoring sites on the southern Eyre Peninsula and southern Spencer Gulf.
  • Highest concentration recorded: 432,899 cells per litre at Proper Bay.
  • Government threshold for “elevated” is >10,000 cells per litre; counts above this suggest an active bloom.

Economic Ripple Effects for Whyalla

The cuttlefish aggregation fuels the town’s winter celebration, “Cuttlefest”, and underpins a multimillion‑dollar tourism sector. Dive‑shop owner Manny Katz reports that the June long‑weekend bookings worth $50,000 were cancelled after the cuttlefish failed to appear, threatening local revenue and community morale.

What Comes Next for the Spawning Season

State researchers will conduct formal surveys in the coming weeks. Doubleday cautions that the next two weeks are critical for determining whether the population will recover or if the bloom will cause a longer‑term collapse. While spawning can sometimes extend into July, the current “anecdotally low” reports raise serious concerns for the future of this globally unique natural phenomenon.