Paaratte commercial eel fisherman Zac Taylor inspected the river on Thursday after fisherman Bill Reddick reported roughly 20 dead cows in the water. Mr Taylor said he counted 25 dead cows.

Mr Reddick said he reported the issue to the Environment Protection Authority Victoria and was told there would be immediate action.

"They were sending someone to investigate. It sounded like they were acting fairly quickly upon it because they were concerned about the dead cattle obviously," he said.

When contacted by The Standard, an EPA spokesman said they had "been to have a look" and decided the toxic conditions were still solely the product of an algal bloom. He said the EPA would only become involved if there were pollutants in the river.

The spokesman declined to say how the EPA reached this decision, nor whether they tested for any pollutants.

IN OTHER NEWS

He said he did not know how the dead cows were related to the toxic river conditions, but that it was all a matter for the Department of Environment, Land, Water and Planning.

A DELWP spokesman echoed the EPA on the cause of the toxic conditions, saying blue-green algae was to blame.

"Blooms of BGA are common in waterways like this due to changes in water levels, nutrient inflows and temperature," he said.

He said nothing could be done about the issue.

"The bloom is expected to take some time to clear until there is significant rainfall and cooler temperatures."

The spokesman reiterated that DELWP had commissioned Wannon Water to test for blue-green algae. He declined to say whether any authorities had tested for pollutants or bacteria that could be traced to sewage.

Dozens of Peterborough locals have been concerned about possible leakage from the nearby sewage treatment farm. The DELWP spokesman said "Wannon Water have confirmed there are no faults" at the farm and had "not received any reports related to sewerage (sic)".

"Authorities are working to determine the death of the cattle and finalise a plan for the safe removal," he said.

Local residents said contrary to the DELWP claims, conditions in the river were far from "common", with one saying he had never seen it so bad.

Warrnambool fisherman Andrew Smith said the scale of the fish kill in the river would cripple the ecosystem.

"There'd been algae down there and a lot of the dead fish were concentrated higher up in the system but this is down literally in and around the town of Peterborough now," he said.

"These bream, which are 36-48 cm, found dead, are potentially 30 to 50 years old, so we're talking potential system collapse."

He said he had little faith in the authorities fixing the problem.

"I know people directly who've been upstream from Boggy Creek and over the years have seen raw effluent just flowing into the river," he said.

Mr Smith said the nutrient levels from farm runoff had been unacceptably high for as long as he could remember, particularly the phosphorus levels.

"This is from the Curdies River monitoring station. The state trigger point for immediate action is 25 micrograms per litre; they've been consistently higher than that since 1990," he said.

"To summarise it it's been a system that's been recognised to need urgent help but been ignored for decades."

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