Whyalla cuttlefish numbers crash amid algal bloom
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- Giant Australian cuttlefish at Whyalla's Spencer Gulf have failed to gather in their usual thousands for the June breeding peak, with divers reporting only "a couple of dozen hanging around, at a couple of different spots" — animals that are "extremely skittish" and hiding under rocks, per Whyalla Dive Shop's Manny Katz.
- Associate Professor Zoe Doubleday of Adelaide University attributes the collapse "on the balance of probabilities" to Australia's first bloom of toxic Karenia cristata algae, which began in March last year and is the largest and most destructive algal bloom in the nation's history; she notes Karenia's effect on cephalopods is "swift and fatal."
- Karenia testing results show elevated levels at 8 of 32 testing sites on the southern Eyre Peninsula and southern Spencer Gulf, with the highest concentration of 432,899 cells-per-litre at Proper Bay; the state government considers levels above 10,000 per litre as "elevated."
- The Whyalla Dive Shop turned away $50,000 worth of bookings for the June long weekend alone, with Katz warning the loss of the aggregation would be "catastrophic" for a world-renowned dive site, and the broader fear is losing the phenomenon itself.
- Historical Cuttlefest numbers show cuttlefish counts ranging from a low of 13,500 in 2013 to 247,000 in 2020, and last year's celebration generated nearly $10m in local spending, highlighting the scale of what is at stake.
- The 15km stretch of coastline 15km north-east of Whyalla where the cuttlefish breed was added to the National Heritage List in 2023, underscoring the site's officially recognised ecological significance.
Why it matters: A heritage-listed breeding aggregation that drew up to 247,000 cuttlefish and nearly $10m in Cuttlefest tourism last year has collapsed to a few dozen animals, with one dive shop already losing $50,000 in June long weekend bookings. The trigger is the largest toxic algal bloom in Australian history, which is still active along South Australia's coastline and described as "swift and fatal" to cephalopods.
