Threatened Species Scientific Committee recommends Maugean skate be listed as critically endangered

Australia’s top advisory body on threatened species has recommended that the Maugean skate be listed as critically endangered after analysis predicted its probability of extinction.

It has been recommended that the conservation status of the Maugean skate be upgraded to critically endangered.

Australia’s Threatened Species Scientific Committee has recommended that salmon farming in Macquarie Harbour be drastically scaled back or even removed entirely to protect the dwindling Maugean skate population.

Environment and Water Minister Tanya Plibersek announced a consultation process relating to the conservation status of the skate on Thursday, saying the independent Threatened Species Scientific Committee (TSSC) had received a nomination from the public to update the listing.

The last known population of the Maugean skate is at Macquarie Harbour, where Ms Plibersek is currently reviewing the future of salmon farming licences amid concerns that aquaculture and other factors are contributing to degraded water quality and reduced levels of dissolved oxygen.

CANBERRA, Australia, NewsWire Photos. June 6, 2024: Minister for the Environment and Water Tanya Plibersek during Question Time at Parliament House in Canberra. Picture: NewsWire / Martin Ollman

It’s estimated that there are only between 40-120 adult skates remaining in the harbour.

Newly published conservation advice from the TSSC recommends that the Maugean skate be transferred from the endangered category to critically endangered, citing a likely 47 per cent decline in “relative abundance” between 2014 and 2021.

“The primary threat to the species is degraded water quality, in particular, substantially reduced levels of dissolved oxygen throughout Macquarie Harbour,” the advice said.

“There is a significant correlation between the reduction in dissolved oxygen levels and increases in salmonid aquaculture due to fish respiration and the bacterial degradation of organic material introduced into the water column from fish-feed and fish-waste.”

The committee described the risk posed by salmon farming to the future survival of the skate as “catastrophic” and recommended that action be taken to “eliminate or significantly reduce the impacts of salmonid aquaculture on dissolved oxygen concentrations”.

“The fastest and simplest way to achieve this is by significantly reducing fish biomass and feeding rates,” it said.

The TSSC also noted the impact of hydroelectric damming on river flows into the harbour, saying it could influence oxygen conditions in the bottom waters. It mentioned recreational gillnetting, climate change, and ongoing heavy metal pollution from historical mining operations upstream as other contributing factors.

In a submission to the federal government’s review of salmon licences, Salmon Tasmania argued there was no scientific evidence to show that removing aquaculture from Macquarie Harbour would ensure the skate’s future and that there was no legal justification for doing so.

A baby Maugean skate has been hatched for the first time in captivity. Picture: Supplied

The salmon industry has pointed to independent modelling conducted by Dr Ian Wallis which it says proves aquaculture has had “minimal impact” on oxygen levels in the harbour.

A population viability analysis conducted last year found that the Maugean skate faced a best-case scenario of 89 per cent population decline by 2041 and a worst-case scenario of a decline greater than 99 per cent “assuming no mitigation of current threats”.

The analysis concluded that the skate had an extinction probability of greater than 25 per cent by the same year.

Ms Plibersek said Maugean skate numbers had almost halved in the past decade and that the federal government had invested $5.7m to help protect the species and improve the health of the harbour.

This included $2.1m to establish a captive breeding program, which this week welcomed the first hatching of a baby skate.

The public consultation process around the conservation listing will be open until September 26.

Opposition spokesman for the environment, fisheries, and forestry Jonathon Duniam said Tasmania’s salmon industry had “the most sustainable practices in the world”.

“A lifeblood of the West Coast is on the line. Tanya Plibersek and Labor must also take into account the social and economic impacts, rather than purely the environmental impacts, before making any rash decisions,” he said.