EPA data on dissolved oxygen in Macquarie Harbour released this week is
represented as having lowered over the last year, and rather than reducing
salmon biomass, the EPA has resolved to order the salmon companies to take
charge of pumping more oxygen into the harbour.
From the report:
“The data indicates that dissolved oxygen levels have declined during the second
half of 2025 and into the first half of 2026,....The EPA has taken prompt steps to
address this and wrote to the three salmon companies in July 2026, requiring an
increase in oxygenation to fully offset their average oxygen demand of 10.3 tonnes
per day as determined by IMAS
” full report here.
The median data points in the report show dissolved oxygen dropping below
the default guidelines and into the ‘red’ in the mid to bottom waters in many
parts of the harbour, including the Tasmanian Wilderness World Heritage
Area. Such low dissolved oxygen levels are considered dangerous to the
survival of the endangered Maugean skate. In 2019, low oxygen levels in the
bottom waters of the harbour during a weather event wiped out around half of
the population, according to scientists. Conservation Advice for the skate has
highlighted that the skate population remains at serious risk from such an
event happening again.
Notably, the averaging of the data used by the EPA could be misleading and
distorting the real risk to the skate. With averaging showing such low levels,
then it’s highly likely that dangerously low levels are being reached temporarily
at times throughout the 12 month period. Even temporarily low dissolvedoxygen levels can be disastrous for the skate and its eggs, which remain
vulnerable for 7 months before hatching.
The Conservation Advice calls for the removal of biomass from the harbour as
an urgent priority. This has been ignored by the federal and state governments
for three years.
Jess Coughlan, Skate campaigner at Environment Tasmania said:
“The Environmental licenses issued by the EPA are still awaiting renewal, after
lapsing in November of 2025. Right now the EPA has the power to solve
this with the stroke of a pen but instead they are kowtowing to industry.
Instead of acting as per the Conservation Advice to alleviate the oxygen
demand pressures on Macquarie Harbour through salmon biomass reduction,
the regulator is deferring to the industry to burn fossil fuels and pump oxygen.
The result is a bandaid solution that is effectively bioengineering the
ecosystem.
”
“Tens of millions of dollars of tax payers money has already been spent on the
oxygenation program to date. The public deserves to know if they will be
continuing to subsidize an industry that is putting the skate, our world heritage,
and the Tasmanian brand at risk.
”
All comments attributed to Jess Coughlan
Senior Campaigner
Environment Tasmania
0431684741