A major role of the Vasse Estuary Technical Working Group (VETWG) is to reduce the frequency and severity of fish kills in the Vasse Wonnerup system. Major fish kills have been recorded in the Vasse estuary since 1905, with the most recent fish kills occurring in April 2013 and February 2014. In most cases the most probable cause of fish kills have been due to algal blooms and poor water quality resulting in low levels of dissolved oxygen.
After the 2013 fish kill, the VETWG developed a Fish Kill Mitigation and Response Plan for the Vasse Wonnerup System. Continuous water monitoring of dissolved oxygen from two loggers installed at the floodgates and daily site inspections support this plan. A major focus of the plan is to respond to environmental conditions to avoid a fish kill by opening fish gates in the floodgates to allow fish to escape into the Wonnerup Inlet. The fish gates are not permanently opened as inflow of salinity has the potential to impact on the Ramsar water bird habitat and surrounding land uses by increasing salinity and water levels in the estuary. The Seawater Inflow Pilot Study into Vasse Estuary is being undertaken by the Department of Water over the 2014/15 summer period to determine the impacts of allowing short periods of seawater inflow on water quality of the estuary.
For more information contact Dr Kath Lynch – District Manager Department of Water 9781 0111.
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