Vasse fish death response update
Released 05 Feb 2014
Estimates of the number of dead fish found near the Vasse floodgates and in the Wonnerup estuary have been revised to more than 10,000.
"The initial inspection on the morning of 4 February showed several hundred fish, and this was later revised to 2000," Department of Water Executive Director Regional Delivery and Regulation Paul Brown said.
"The latest estimate of numbers as of 3pm on 5 February, which includes clean up statistics from the City of Busselton, is more than 10,000.
"The fish are all mullet and they have been found at locations near the Vasse floodgates and in various locations in the Wonnerup estuary and inlet.
"Estimates generally increase during fish death responses as more fish float to the surface, and a final estimate using surveys and clean up statistics will be issued upon completion of the inter-agency response.
"The Department of Fisheries has begun pathology tests and it will take up to five days before results are available.
"Our monitoring equipment shows that dissolved oxygen levels in the system had been inside 'trigger levels' up to and through the period where the fish have died.
"There were also no reports of fish milling at the floodgates which is an indicator of low dissolved oxygen leading to a fish kill.
"Our water quality report of Monday 3 February picked up the high density levels of the algal species Prymnesium, which can be toxic to fish. This species was not detected in the previous algae sampling tests two weeks before and is likely to have been a significant contributor to the fish deaths.
"As part of the 2013-14 summer fish kill mitigation and response plan, floodgates were opened by the department and the Water Corporation to allow any fish trapped in the affected area to move into the Wonnerup inlet and out to sea.
"The Vasse Estuary Technical Working Group members (City of Busselton, Water Corporation and the Departments of Fisheries, Water and Parks and Wildlife) responded quickly to this incident and have followed the inter-agency fish kill mitigation and response plan.
"The City of Busselton has led the fish clean up and arranged for water oxygenation plants to be operating.
"The Water Corporation has previously opened the sand bar and opened the flood gates yesterday.
"The Department of Water is coordinating the response and monitoring water quality and Fisheries is undertaking the fish pathology testing."
Contact with dead fish should be avoided and the Department of Health advises against eating or handling of fish found in these circumstances, and recreating in waterways during a fish kill or algal bloom event.
People are asked to report any fish deaths to the Department of Fisheries Fishwatch on 1800 815 507.
Contact: Peter Collins
Phone: (08) 6364 6848 / 0434 603 441