Algae behind Cockburn Sound fish death mystery

[Australia] Authorities believe they have solved the mystery surrounding the deaths of hundreds of fish in Cockburn Sound, saying the mass-kill was likely caused by a bloom of microscopic algae.

Since November, more than 1500 dead snapper and blowfish have washed ashore while at least one dead shark, eel and starfish have also been reported to have washed up in the same area.

On Tuesday, dive instructor Jason Santospirito told Radio 6PR since the fish deaths the underwater area, which used to be swimming with fish, looked like “a ghost town”.

Department of Fisheries supervising scientist Michael Snow said the deaths were likely caused by a naturally occurring algae, called Chaetoceros spp, which is known to cause gill irritation in fish and can lead to respiratory failure.

The bloom, which is not harmful to humans, was likely to have been sparked by warmer water temperatures around the time of the fish deaths.

“Similar diatoms have been implicated in fish death events in other parts of Australia and also internationally,” Dr Snow said.

“This bloom may also have been associated with low dissolved oxygen conditions which are known to periodically occur in southern sections of Cockburn Sound placing extra stress on the fish.”

The announcement of the likely cause of the fish deaths comes after authorities tested specimens for more than 120 algal toxins and industrial contaminants including heavy metals, fertilisers, pesticides and hydrocarbons.

Mr Santospirito claimed fish in the Sound had “disappeared” compared to earlier in November when it was common for more than 60 fish to be visible during a 10 metre dive.

“[After the fish deaths] we started noticing all the big fish were gone, the juvenile snapper were all gone …all our line fish had disappeared but we saw the little ones were still about,” he said.

“We go back on December 6 and the little ones are dead with their mouths gasping for air all on the bottom of the Sound.”

The Department of Parks and Wildlife had previously ruled out a dead fairy penguin and pelican as casualties of the mystery mass deaths, saying the penguin likely died of starvation.

The accidental spill of half a tonne of canola grain into the Sound by CBH Group in November was also ruled out as a contributor to the deaths.

The Department of Fisheries plans to release a public report on the findings.


Photo: Recfishwest chief executive Andrew Rowland with a dead pink snapper at Cockburn Sound. Photo: Recfishwest

View original article at: Algae behind Cockburn Sound fish death mystery

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