Scientists urge action to protect habitat of Tasmania’s endangered ancient skate
Scientists studying Tasmania’s endangered maugean skate believe urgent action is needed to help the species survive in Macquarie Harbour, which hosts the only surviving population of the ancient fish.
Tasmanian Institute for Marine and Antarctic Studies (IMAS) scientists have been monitoring falling oxygen levels in the harbour.
They said declining environmental conditions due to salmon farming and changes in river flow have been piling pressure on the species.
They believed a reduction in the salmon stocks and fallowing pens may be necessary if environmental conditions continued to deteriorate, to ensure the skate’s survival.
Falling oxygen levels in the harbour sparked an alarm two years ago, identified by IMAS as a “major deterioration” event, and initial studies identified that fish farm waste was a significant factor.
“We know that oxygen in the harbour has been decreasing over the last 10 years and that’s raised some concerns about the maugean skate since it’s an endangered species,” researcher Dr Killian Stehfest said.
An interim finding from the ongoing study warned:
Given the potentially limited genetic capacity of this small and spatially restricted population to adapt to changes occurring in the environment, there is an urgent management need to limit and reverse any further deterioration of benthic conditions in Macquarie Harbour which have the potential to impact the availability of favourable habitat and food sources of the Maugean skate.
Moreover, recognising that localised extinction may have occurred in Bathurst Harbour, a remote and pristine environment lacking anthropogenic pressures, any additional anthropogenic threats to the species in Macquarie Harbour could increase the risk of global extinction of the species.
Dr Stehfest is part of the team conducting the first detailed study of the skate, which was only discovered in 1988.
Killian Stehfest with the cutting-edge tag being used to track the endangered maugean skate. (ABC News: Henry Zwartz)
“What we are hoping to do is get a clear picture of the health of the species and how much time it spends in different areas which have varying levels of oxygen. That will give us a picture of how it is coping with declining oxygen rates,” Dr Stehfest said.
“It’s a very interesting species, because it’s the only skate species that spends all its life in brackish water and its also the skate with the smallest range out of any skate species.”
As part of the study he has been he has been catching them and fitting them with an electronic tag, the first of its kind to be used on a wild animal which measures oxygen levels underwater at different depths.
The tag transmits the data to “listening stations” deployed underwater, which are then available in real time.
“It’s exciting to be using this technology on a species, it’s a world-first in many ways,” Dr Stehfest said.
Adding to concerns by experts is a recent genetic study which shows the skate has a limited genepool.
Associate Professor Jayson Semmens believes this makes the species even more vulnerable.
“If the environment kept changing then their ability to move away from low oxygen would decrease,” he said.
“It’s a sad day when any species goes extinct and that has happened in all our lifetimes. It happens more regularly than we would like, so absolutely, it would be a sad say if it went extinct.”
Scientist Jeremy Lyle, an author of the genetic study, said reducing salmon numbers and rotating empty pens could help, a practice in farming known as “fallowing”.
“We want to ensure that the habitat and its broad environment there is suitable for it to persist into the future,” he said.
“Preliminary research suggests the fish has limited ability to tolerate low oxygen levels.
“The environmental health of the harbour is likely to be a crucial factor in the future wellbeing of the maugean skate,” he said.
The experts hope the skate’s future is less murky than the waters it inhabits.
The results of the study — which is partly funded by large salmon companies, alongside federal and state government departments — are expected early next year.