A study of fish and mussels in Claisebrook Cove has uncovered alarming rates of male fish with male and female sex organs, DNA damage in mussels and other evidence suggesting exposure to high concentrations of pollutants.
The study by researchers at Curtin University looked at fish health in the cove and found unprecedented rates of intersex (having both ovaries and testes) in black bream, a popular target species for recreational anglers.
The snapshot study found 13 per cent of the male black bream sampled had male and female sex organs that could be observed without the use of a microscope.
Co-author of the study, eco-toxicologist Monique Gagnon from Curtin, said intersex in black bream had only ever been recorded once in 10 years of studies in the Swan and Canning rivers.
Associate professor Gagnon said overseas studies had recorded fish developing male and female gonads in highly polluted environments.
She said the Claisebrook findings suggested fish were being impacted by contaminants and more research was urgently needed to discover the extent of the problem and whether fish were being impacted in other areas of the river system.
Although more than a year old the study, prepared for the Swan River Trust, has yet to be released publicly.
It was done in conjunction with a second report, by the Department of Water, on contamination in Claisebrook Cove leaked to The West Australian last week.
That report found high levels of contaminants in fish and mussels.
Claisebrook Cove abuts the old East Perth gasworks, a known contaminated site and is the end point of a major unfiltered drain.
A spokesperson for the Swan River Trust said further studies were underway to determine whether there was any ongoing sources of contamination entering the river system.