- Maugean skate does not have time for slow improvement in oxygen levels - only 40-120 adult skates left in the harbour
- Oxygen levels still low in deep waters - an upturning of deep, oxygen-depleted waters wiped out nearly half the Maugean skate population in 2019
- Removing salmon farming is the fastest way to improve oxygen levels for the skate to survive and recover
The precariously low numbers of Maugean skates are facing extinction in their only home, Macquarie Harbour, because of the low oxygen levels in the harbour, the Australian Marine Conservation Society said after Tasmania's Environment Protection Authority released a report showing gradual improvement in the harbour's oxygen levels.
The Federal Government's Conservation Advice recommended reaching pre-2009 dissolved oxygen levels by 2024, but that is likely to be years away despite the recent upwards trend. The trend can be attributed to reductions in salmon biomass production from its peak in 2015 along with natural oxygen recharging from sea water entering the harbour last summer.
In the deeper waters of Macquarie Harbour oxygen levels are still not at the level where the Maugean skate can safely live. It was the upturning of deep, oxygen-depleted waters from storms that wiped out nearly half the Maugean skate population in 2019.
AMCS Fisheries and Threatened Species Campaign Manager Alexia Wellebelove said: "The Maugean skate is on the brink of extinction, it does not have enough time to wait for the oxygen levels to slowly recover to the levels they need to live and survive. There are only an estimated 40-120 mature adult skates left in Macquarie Harbour and its extinction could be in as little as 10 years' time, possibly earlier if a big storm creates another upturning event. Any introduced skates from the breeding program will face the same extreme conditions these last remaining adults face.
"Salmon farming has dramatically depleted the oxygen levels in Macquarie Harbour, and removing salmon farming is the fastest way to improve oxygen levels for the skate to survive and recover.
"Salmon stocks in Macquarie Harbour peaked in 2015 at about 20,000 tonnes - the equivalent mass of about 1000 humpback whales. The salmon industry has not reduced biomass far enough in that time, so the federal government needs to act on its own Conservation Advice, which recommended the removal of salmon last summer.
"The Albanese government has made a commitment to zero new extinctions. We are calling on Environment MInister Tanya Plibersek to see that salmon farming ceases in the harbour to meet this commitment and ensure the skate's survival.
"Macquarie Harbour is part of Tasmania's World Heritage Area and integral to the state's reputation for natural beauty and conservation. The extinction of the Maugean skate would be a devastating blow to Australia's biodiversity and to Tasmania's brand and natural heritage."
