Hundreds of black bream and mullet have been killed by an algal bloom in Marbellup Brook over the past week.
The algal outbreak, 15km west of Albany, has prompted action from authorities after nearby residents voiced concerns for their health and complained about the stench of rotting fish.
About 1.4km of the brook along Elleker-Grassmere road is affected by the bloom.
Brook Street resident of 25 years and Torbay Catchment Group member John Blaney-Murphy described the bloom as the worst since he moved to the area.
“We can’t hang washing on the clothes line because the smell gets all through it; I’ve never seen so many dead fish,” he said.
Trevor McGonnell lives near the brook and likened the smell of the bloom to “raw sewage” and said after living with the problem since 1995, it had to be fixed.
Department of Water south coast region manager Brett Ward said reduced rainfall and flows in inland waterways over summer increased the potential for algal blooms, with the risk of increased growth in river pools as they dry and stagnate.
The department has tested the brook water and found high turbidity and little or no oxygen.
“Fish kills most commonly occur from a lack of oxygen in the water which is caused by the decomposition of algae and not necessarily as a result of algal toxicity,” Mr Ward said.
Phytoplankton analysis to determine the type of algal bloom was underway yesterday.
The dead fish have been cleaned up and the City of Albany has placed warning signs at the brook.After a visit to the affected site on Monday, Water Corporation’s Great Southern regional manager David Hughes-Owen said a pumping operation would be installed by the end of the week to improve water circulation, and could remain in place for up to two months.