‘Tinkering with toys’: Salmon industry fund oxygen trials to save endangered Maugean skate

The Salmon industry will invest millions to manufacture increased oxygen levels in Macquarie Harbour, but Bob Brown Foundation says they’re not doing it for the Maugean skate.

The salmon industry will invest millions of dollars to manufacture increased oxygen levels in Macquarie Harbour in an effort to save the endangered Maugean skate.

Salmon Tasmania has teamed up with Australian Government’s Fisheries Research and Development Corporation (FRDC) and the Institute for Marine and Antarctic Studies (IMAS) to place a barge on the harbour to manufacture an increased level of oxygen.

The $6m two-year project will start this summer for a first trial as part of a “long term strategy”.

SUN TAS. Luke Martin who has stepped down as CEO of the Tourism Industry Council Tasmania to take up a role with as Salmon Tasmania chief. Picture: Nikki Davis-Jones

“It’s important to recognise there are a range of factors influencing the oxygen levels in the Harbour and the decline of the skate, which is widely accepted as now extinct in Bathurst Harbour where there is obviously no aquaculture,” Salmon Tasmania chief executive Luke Martin said.

“The industry has more than halved its biomass levels in Macquarie Harbour since 2017, and this has had no apparent impact on the dissolved oxygen levels in the water system. Clearly the issues are far more complex than simply removing the salmon.”

But the Bob Brown Foundation said the investment doesn’t mitigate or undo the damage caused by aquaculture.

Public Forum: Industrial Salmon in Tasmania, Bob Brown Foundation Fish farm campaigner Alistair Allan. Picture: Chris Kidd

“The only reason we’re in this situation in the beginning is because of how much they’ve abused fish farming in Macquarie Harbour,” Antarctic and marine campaigner Alistair Allan said.

“The oxygen level collapsed in 2017 because of fish farming … so you take all the oxygen away in the initial event, and then you want to try and come back, they need to get out and give time for the ecosystem to recover.

“The industry didn’t choose to half it on behalf of the skate, but the industry almost collapsed and that’s why they halved it.”

A research team will draw water from the sea at depth from a barge on Macquarie Harbour. Through “passive diffusion” and “natural mixing”, the team will inject highly concentrated micro and nano bubbles of oxygen into the drawn water and then release it back into deeper water sections.

Salmon farming pens in Macquarie Harbour, Tasmania. Photo: Eloise Carr

“This technology is used successfully in marine environments all over the world, including in a major project running over the past twenty years to support Perth’s Swan River estuary,” Mr Martin said.

“At a minimum, we aim to offset the total oxygen drawdown of our own salmon aquaculture activities in the Harbour, and further reduce the impact of our operations on the environment.”

But Mr Allan said the industry has pushed harder than beyond its limits.

“We can’t be in there tinkering with toys and left with left of field ideas about mechanical engineering for a harbour that’s six times bigger than Sydney Harbour,” he said.