Whyalla wipeout fears: cuttlefish usually gather in their thousands, but few have appeared since a massive algal bloom

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Only a few dozen giant Australian cuttlefish have appeared along the Cuttlefish Coast near Whyalla by mid-June, the usual peak breeding period when thousands to hundreds of thousands normally gather. The near-absence coincides with the continued presence of Australia’s first bloom of toxic Karenia cristata algae, which began in March 2025 and remains at elevated levels at eight of 32 testing sites in southern Spencer Gulf, with concentrations reaching 432,899 cells-per-litre at Proper Bay against a 10,000 cells-per-litre threshold. Formal government surveys are still to be conducted, but researchers report anecdotally that population numbers appear relatively low.