"There were dead fish on the banks up and down the creek. Some of them were big silver bream," Mr Jeffries said.

"They were beautiful fish that could be breeding."

He noticed a stench coming from the creek before Christmas.

"There was sludge. The water was turbid. It wasn't going anywhere. The water was brown, almost as bad as the Yarra. Previously it was clear and you could see the fish swimming. Now the stench is overpowering."

The Environment Protection Authority confirmed it is investigating reports of the dead fish. Officers discovered more than 100 fish in the creek yesterday.

"While there are no obvious signs of pollution, EPA has taken water samples and is awaiting analysis," spokeswoman Ruth Ward said yesterday.

"It is possible the fish have died as a result of natural causes. Melbourne Water will clean up and dispose of the fish."

Last week, surveying, planning and engineering contractor Aurecon was carrying out flood survey work for Melbourne Water in Kananook Creek and its tributary Eel Race Drain between Patterson Lakes and Beach Street, Frankston.

James Watts of Aurecon said the six-wheel amphibious craft he and his associate were using kept getting stuck in the thick sludge in the creek.

He said Melbourne Water had cut off the pumps that fed water from Patterson Lakes into Eel Race Drain while it was carrying out dredging and replacing a diversion weir behind the Riviera Hotel in Seaford.

Mr Watts said the level of the creek was very low. "We have asked Melbourne Water to turn on the pump so we can continue our work."

Kananook Creek Association president Rob Thurley said the pumps "could be seen as the artificial heart of the creek". He said it appeared the pumps had broken down last month, effectively stopping the creek flow.

Mr Thurley said his association wanted Melbourne Water to regard the creek as a recreational waterway, not a drain.

"Murky water from the creek is contaminating Frankston's award-winning beach."

KCA secretary Olwyn Bawden believes the fish kill is the result of low water flows and unlikely to be caused by sediment.

"We've had fish kills before and it's usually a combination of low water and heat."

Melbourne Water spokesman Nicolas McGay confirmed the pump had broken down.

"The creek is reliant on artificial flows. The pump failed and the combination of low water oxygen levels and heat led to the fish kills."