EPA scientists have again reviewed long term data sets to create a status update report for dissolved oxygen levels in Macquarie Harbour. The September 2024 report shows that the trend of improving oxygen levels in the middle and deeper waters of the harbour have reached new heights.
EPA Director, Wes Ford, said the median dissolved oxygen levels across Macquarie Harbour are at their highest levels in more than a decade.
“Our scientists have used two independent data sets that have hundreds of data points across multiple sampling locations throughout the harbour, and I am pleased to report that two thirds of Macquarie Harbour now has dissolved oxygen levels within the range observed from 1993 to 2010," Mr Ford said.
The data is collected through a monthly broadscale environmental monitoring program that salmon companies are required to undertake, and the EPA's own quarterly monitoring program which has been ongoing since 1993. Both data sets show an overall improvement in dissolved oxygen levels.
For shallow waters, the southeastern segment of the harbour also shows dissolved oxygen levels in line with the range observed from 1993 to 2010. Below 16m depth, dissolved oxygen levels in the southeastern segment are now close to the historical range, with some further improvement needed.
The Macquarie Harbour Oxygenation Project is currently trialling technologies that are expected to sustain and further improve oxygen levels across the harbour. The salmon industry is finalising oxygen mitigation plans, which are due to be submitted to the EPA for approval in the coming days.
Commencing in 2017, the EPA Director progressively cut the scale of fish farming in Macquarie Harbour by half. “It is very encouraging to see that oxygen levels in Macquarie Harbour can improve while fish farming remains at this scale," said Mr Ford.
Macquarie Harbour - Status update for dissolved oxygen - September 2024 (PDF 1Mb)
Published on:
13/09/2024