Endangered Maugean skate die in captive breeding program
Maugean skate numbers have been decreasing significantly in Macquarie Harbour — their only known home — coinciding with an increase in salmon farming. In an attempt to prevent their extinction, a captive breeding program was funded by the state and federal governments, but two out of four skates have already died. Scientists do not plan to capture any more adult skates for the program but over the next few months will continue to monitor fifty eggs they also captured.
Creating an "insurance population" was seen as essential in preventing the extinction of a species of ray that only lives on Tasmania's west coast, but the project has immediately encountered setbacks.
Scientists at the Institute for Marine and Antarctic Studies (IMAS) collected the four adults from Macquarie Harbour on December 15, but two did not survive.Program leader Professor Jayson Semmens said it was unclear why they had struggled in captivity.
Skate numbers almost halved between 2014 and 2021, with fewer than 1,000 left in the wild, due to reduced levels of dissolved oxygen in Macquarie Harbour. Conservation advice provided this year to the federal government, which is reconsidering salmon licences in the harbour, found that the issues around dissolved oxygen were predominantly caused by salmon farming.
"It's a cautionary tale of what can happen to these specialist animals that only live in one or two places in the world," Professor Semmens said. "The end game does need to be they go back into the wild."
Last year, conservation advice to federal environment minister Tanya Plibersek said that the quickest way to improve conditions in the harbour was a further reduction in salmon farming by this summer.
That de-stocking did not occur, and the captive breeding program was established instead, along with a trial for a diesel-powered oxygenation system, mostly funded by the salmon industry.
The federal government announced $2.1 million to help establish the captive breeding program in September. This funding was matched by the Tasmanian government in November.
The Commonwealth is in the process of considering the renewal of farming licences in the harbour — and has warned salmon farming could be paused — after requests were made by the Australia Institute, Bob Brown Foundation and Environmental Defenders Office.
In a follow-up interview, Bec Howarth, Environment Tasmania, praised the skill and dedication of IMAS scientists on this project, but said that, fundamentally, the captive breeding program was too little, too late, and that the best way to save the skate is to immediately remove salmon farms from Macquarie Harbour. Listeners texting the ABC overwhelmingly agreed.