Cause of mass fish deaths in Cockburn Sound unknown

“We’d love to see any people responsible held to account and prosecuted,” Recfishwest chief executive Andrew Rowland said.

By the end of last week, there was no proof the deaths of at least 700 snapper, whiting, flathead and other species found badly decomposed on east and west coast beaches in the Sound were linked to pollution or a human cause.

“And it’s not heavy metals because they generally accumulate over time and this happened suddenly,” Mr Rowland said.

He said WA’s 740,000 fishers represented by the lobby were horrified about the kill’s potential impact on breeding pink snapper, their larvae and eggs, which are protected in the Sound while the species spawns, until January 31.

To date tests have found no evidence of a chemical source being responsible for the deaths.

Biosecurity research scientist Michael Snow said tests on water and fish tissue samples from the Sound had been inconclusive but they did indicate elevated levels of a naturally-occurring bacterium that may be harmful to fish.

However, this was unlikely to be the primary cause.

After the deaths, Kwinana-based titanium feedstock maker Tronox said in a statement it had recently analysed its process, confirmed all its materials were accounted for and there had been no loss of contaminants from its plant.

A spokeswoman for the nearby Alcoa refinery said there was nothing to suggest its operations were connected to the fish deaths and any contrary speculation was “highly inappropriate”.

Checks are also under way into reports earlier this week of large numbers of dead blowfish and some dead snapper on both sides of the Garden Island Causeway and near Point Peron boat ramp.

“Staff members from our Fish Health branch have been collecting samples of the blowfish to see if we can get some gills in testable condition to help assess whether there is any new evidence of what has caused the deaths,” Dr Snow said.

“We regularly remind people not to swim or fish in water that looks discoloured, murky, or smells unpleasant, or where there are large numbers of dead fish, so they need to apply that advice in areas where dead fish are located,” he added.