More than 8,200 sharks and rays were reported dead during an algal bloom off the South Australian coast, a toll one researcher says is probably the largest mass mortality of these animals ever recorded, with rare species possibly facing extinction.
The deaths were documented by the Great Southern Reef Foundation, which drew on thousands of citizen scientist reports of animals washed ashore during the bloom. Unreported deaths mean the true toll is likely much higher, and the recorded count included around 4,500 southern fiddler rays, 850 Port Jackson sharks and 670 wobbegongs.
Among the species in the bloom's path is the pygmy thornback skate, photographed by diver David Muirhead in about three metres of water off Edithburgh Jetty during the early days of the bloom. Muirhead, who said he has completed around 2,000 dives in South Australian waters, described the sighting as possibly witnessing the end of a species. The skate's range is mostly confined to the affected waters, and the coastal stingaree, listed as endangered by the International Union for Conservation of Nature, faces a similar problem. "For some of these species that have a naturally low abundance, or have a very restricted range that overlaps with the algal bloom, we could be looking at some level of extinction," said Charlie Huveneers, director of the Flinders University Marine and Coastal Research Consortium.
Neither species is considered threatened under federal law. A spokesperson for the environment department said any person can nominate a native species for assessment under the Environment Protection and Biodiversity Conservation Act, and that the 2026 assessment cycle included a conservation theme for nominations supporting the protection and recovery of species at risk from the harmful algal bloom. No nominations were received for either species, the spokesperson said. The spokesperson said assessments require scientific evidence, and insufficient data had impeded the department's ability to assess population status.
Huveneers' own tagging research paints a bleak picture for metropolitan populations: of more than 150 sharks and rays tagged before the bloom, none had returned 12 months later. He said sharks and rays reproduce slowly, taking a long time to mature, and that populations from unaffected areas may move in. Muirhead said he is seeing recovery in many common bony fish species and marine invertebrates, but has seen only one ray since the bloom. Huveneers said he hopes people will start seeing sharks and rays again, but it might take a while to get to the numbers they used to have.
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Shark and ray deaths reported during SA algal bloom
individuals
Unreported deaths mean the true toll is likely much higher. Source: Great Southern Reef Foundation
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Analysis
Why This Matters
The bloom may have pushed species with small ranges, such as the pygmy thornback skate, toward extinction.
Local populations of common sharks and rays may have collapsed, with none of more than 150 tagged animals returning a year after the event.
Recovery will be slow because sharks and rays mature late and reproduce infrequently, so the effects could last years.
Background
The harmful algal bloom that hit the South Australian coast earlier in 2026 prompted a large citizen science effort, with thousands of reports of dead animals washing ashore. The pygmy thornback skate is so rare it is usually only seen when fishing trawlers pull it up, and its range overlaps heavily with the affected waters. Sharks and rays are slow-growing, late-maturing animals with small litters, which makes their populations particularly vulnerable to mass mortality events.
Key Perspectives
David Muirhead, recreational diver: photographed a pygmy thornback skate during the bloom and said he felt sad because he was likely witnessing the end of one species; he has seen only one ray since the bloom.
Charlie Huveneers, Flinders University researcher: calls the die-off the largest mass mortality of sharks and rays ever recorded, warns of possible extinction for restricted-range species, and says recovery will be slow.
Environment department spokesperson: says anyone can nominate a species for assessment, but no nominations were received for the two rays and insufficient data has prevented assessment.
What to Watch
Whether the pygmy thornback skate or coastal stingaree is nominated for threatened species assessment in future cycles.
Whether shark and ray populations begin returning to the affected waters in coming seasons.
Whether the department obtains the scientific evidence needed to assess population status for the affected species.
12 claims in this story checked against 1 source: 11 supported.
Show each claim
SupportedMore than 8,200 sharks and rays were reported dead during the bloom.Just In: “More than 8,200 dead sharks and rays were reported during the bloom.”
SupportedHuveneers says the toll is probably the largest mass mortality of sharks and rays ever recorded.Just In: “"That's probably the largest mass mortality ever recorded for sharks and rays," Professor Huveneers said.”
Partly supportedRare species may face extinction because of the bloom.Just In: “"For some of these species that have a naturally low abundance, or have a very restricted range that overlaps with the algal bloom, we could be looking at some level of extinction," said Charlie Huveneers”
SupportedHuveneers said: “For some of these species that have a naturally low abundance, or have a very restricted range that overlaps with the algal bloom, we could be looking at some level of extinction,”Just In: “"For some of these species that have a naturally low abundance, or have a very restricted range that overlaps with the algal bloom, we could be looking at some level of extinction," said Charlie Huveneers, director of the Flinders University Marine and Coastal Research Consortium.”
SupportedThe Great Southern Reef Foundation compiled thousands of citizen-scientist reports of dead animals washed ashore during the bloom.Just In: “Earlier this year, the Great Southern Reef Foundation pulled together thousands of entries for citizen scientists during the bloom, recording dead animals that had washed ashore.”
SupportedAround 4,500 southern fiddler rays were reported dead.Just In: “Around 4,500 southern fiddler rays, 850 Port Jackson sharks and 670 wobbegongs were reported dead.”
SupportedAround 850 Port Jackson sharks were reported dead.Just In: “Around 4,500 southern fiddler rays, 850 Port Jackson sharks and 670 wobbegongs were reported dead.”
SupportedAround 670 wobbegongs were reported dead.Just In: “Around 4,500 southern fiddler rays, 850 Port Jackson sharks and 670 wobbegongs were reported dead.”
SupportedThe coastal stingaree is considered endangered by the IUCN.Just In: “It is a similar problem for the coastal stingaree, considered an endangered species by the International Union for the Conservation of Nature.”
SupportedNeither the pygmy thornback skate nor the coastal stingaree is considered threatened under federal law.Just In: “But neither the pygmy thornback skate nor the coastal stingaree are considered threatened species by the federal government”
SupportedThe department spokesperson said no nominations were received for either species.Just In: “"No nominations were received for the pygmy thornback skate or coastal stingaree."”
SupportedOf more than 150 sharks and rays tagged before the bloom, none had returned 12 months later.Just In: “"Out of the more than 150 sharks and rays we tagged before the bloom, 12 months later none have returned," he said.”
