Cockburn Sound fish kill likely cause found

A Recfishwest officer investigating dead fish washed up in Cockburn Sound.
A Recfishwest officer investigating dead fish washed up in Cockburn Sound.

THE Department of Fisheries has confirmed a bloom of microscopic algae likely caused recent fish deaths in Cockburn Sound.

Supervising scientist Michael Snow said testing had isolated a spike of a group of algal diatom species Chaetoceros spp. which have spines made of silica and are known to cause gill irritation in fish that can lead to mucous accumulation and respiratory failure.

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

“This bloom may also have been associated with low dissolved oxygen conditions which are known to periodically occur in (the) southern section of Cockburn Sound, placing extra stress on the fish. Fish death events often involve multiple contributory factors that make cases difficult to solve.”

Dr Snow said the patience of the community was “appreciated” while the investigation was undertaken and other potential causes were eliminated.

“We cannot afford to jump to conclusions in these cases which must be based on solid scientific evidence,” he said.

“Investigations have included screening for a wide range of over 120 algal toxins and industrial contaminants including heavy metals, fertilisers, pesticides and hydrocarbons.”