The deaths have angered anglers and Princetown residents, who have slammed authorities’ decision to open the Gellibrand River estuary at Princetown.
An Environment Protection Authority spokeswoman said the EPA was aware of the deaths and had contacted the Corangamite Catchment Management Authority, which will investigate further.
The CCMA says fish such as black bream, estuary perch, yellow-eyed mullet and smaller species died after Parks Victoria opened the estuary to the ocean last week.
CCMA river health executive manager Trent Wallis said the number of dead fish was likely to be in the thousands.
“Exact numbers are difficult to ascertain due to high levels of predation from birds and many fish being washed out to sea,” he said.
Mr Wallis said a combination of “very low” tides and high water levels in the estuary appeared to have resulted in faster water flows from the river mouth than the CCMA expected.
He said the estuary levels dropped by up to 1.5 metres overnight because of a lack of replacement flows, and low oxygen levels in the water suffocated the stranded fish.
“This combination of low tides and low flows into the estuary from the river, combined with the continuing degradation of water in the closed estuary, has not been encountered before,” Mr Wallis said.
“This improved understanding of the risks to the Gellibrand system will be taken into account for future decisions,” he said.
An Apollo Bay angler, who wanted to be anonymous, said he found hundreds of dead fish along a three-kilometre stretch of the river on Sunday.
“There were 60 to 70 larger fish, at a guess, and small bait fish would probably run into the hundreds,” he said.
“There were dead fish lying on the boat ramp in the carpark where everyone pulls up.
“It’s not something that’s going to rejuvenate over a short amount of time; it’s going to have effects over a lot of years to come.”
Princetown landholder Matt Bowker said opening the estuary earlier could have avoided the “appalling” fish deaths.
“It’s always a tough call
on when to open it but it’s so severely affected by the amount of water taken out of the top end of it for Warrnambool,” Mr Bowker said.
“I would’ve said three weeks earlier that it was time to let it go and if it meant that after a week it blocked up again, then so be it,” he said.
The CCMA provides advice on the estuary openings and Parks Victoria assesses the advice before deciding whether to open the river mouth.
Mr Wallis said CCMA recommended opening the estuary to avoid fish from dying in a closed estuary, and to reduce the risk of flooding on private land.
By Jennifer Chiu, March 1st 2013
http://www.colacherald.com.au/2013/03/river-opening-kills-thousands-of-fish/
Assessment of Environmental Flow requirements for the Gellibrand River July 2006
http://ccma.vic.gov.au/gellibrand/Recommendations_Final.pdf
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