The Maugean skate, Zearaja maugeana is being threatened by pollution caused by salmon farming in their Macquarie Harbour habitat in Tasmania. The Federal Government allocated $28.6m in the Mid-year Economic and Fiscal Outlook to aid the skate’s protection. A successful captive breeding program has reportedly seen an increase in the number of babies.
According to the Sydney Morning Herald newspaper, “The future of salmon farming in Macquarie Harbour, on Tasmania’s remote west coast, has been uncertain since 2023, when environment groups challenged the government’s approval for the industry due to its impacts on the critically endangered Maugean skate.”
(Source: Maugean skate (Zearaja maugeana) – Australian Marine Conservation Society)
On 26th March, “Greens environment spokeswoman Sarah Hanson-Young staged a piscatorial stunt to accuse the government of “gutting” environment laws and driving an endangered native species to extinction.”
Despite Hanson-Young’s protest, a controversial salmon bill was passed by the Senate after the Lower House passed legislation allowing salmon farming to continue in Macquarie Harbour. The legislation also tightens the rules around reviewing prior government decisions.
It would seem then that the future of the Maugean skate is now bleak at best. Here are a few background details regarding the skate: –
Dr David Moreno, Research Fellow Fisheries, University of Tasmania, Institute for Marine and Antarctic Studies, has authored/co-authored several papers of relevance to the Maugean skate, including “Movement, habitat utilisation and population status of the endangered Maugean skate and implications for fishing and aquaculture operations in Macquarie Harbour”. This photo features in that paper: –
(Source: “Movement, habitat utilisation and population status of the endangered Maugean skate and implications for fishing and aquaculture operations in Macquarie Harbour” by Justin Bell, Jeremy Lyle, Jayson Semmens, Cynthia Awruch, David Moreno,
Suzie Currie, Andrea Morash, Jeff Ross and Neville Barrett)
According to iNaturalist , “The Maugean skate or Port Davey skate (Dipturus maugeanus) is an endangered species of fish in the family Rajidae. Also known as the ‘thylacine of the sea’. It is endemic to Tasmania, only found in the brackish estuarine waters of Macquarie Harbour and Bathurst Harbour. The species was discovered in 1988 by Dr Graham Edgar. It was named in honour of René Maugé, a zoologist on the Baudin expedition to Australia, who died in Tasmania in 1802*. The skate is recognised as one of the Gondwana-era natural values of Tasmania’s Wilderness World Heritage Area. Its potential extinction carries global significance.”
* (He died just before midnight on 20th February 1802. According to Tasmanian Seafarers’ Memorial , “Zoologist René Maugé aged 42 sailed on Le Geographe with his friend Nicolas Baudin. Maugé became ill with dysentery contracted whilst the ship was in Timor and died on arrival in Van Diemans Land.” He was buried with full military honours. Point Mauge in Tasmania is named after him.)
There is a Healthy Harbour Project on iNaturalist. A posting of a skate egg case can be found at https://www.inaturalist.org/observations/251219847 .
According to “Maugean Skate Debate Update” by Michael Jacques in MARINE Life magazine for Autumn 2024, however, “In January we also had the slightly negative story that the captive breeding program had suffered a setback. Two of the four adult endangered Maugean skates taken into an Institute for Marine and Antarctic Studies (IMAS) captive breeding program on December 15 died. It was expected that at worst there was only a 50/50 chance that one might die.
“Scientists also took 50 eggs to the IMAS facility in Taroona, where they were kept in water that had improved dissolved oxygen levels compared to the harbour. Professor Semmens said the captive breeding program “comes with risks”, but it would continue as the eggs hatch over the coming six months.”
The government’s recent budget provides for an additional $3m towards the skate’s protection. The Australian Marine Conservation Society, however, recently said, “The Albanese Government is pushing legislation that would make it easier for industries like salmon farming to avoid scrutiny—at the expense of threatened species.”
According to “Our submission to the Federal Government on Maugean Skates” in MARINE Life magazine for Autumn 2024, “The science research reports have been out for some time and IMAS (Institute for Marine and Antarctic Studies) has issued warnings about the imminent extinction of the Maugean skate some time ago.
“The Maugean Skate is the world‘s only skate known to inhabit brackish water. The species inhabits low-nutrient brackish water, 5–7 metres deep in the shallower upper regions of Macquarie Harbour. The total range of the species is thought to be no more than 100 km2 and the population is estimated at 1000 individuals. “There’s no other shark or ray that lives in such a confined area,” Professor Edgar recently said.
“Dr Neville Barrett said, “We are aware that the harbour isn’t – as some people perceive it – a highly impacted estuary from the mining activities”. “It’s actually quite pristine, the vast majority of it, and it’s an extremely important habitat of course for this species that lives nowhere else on earth.”
Dr Barrett, University of Tasmania, Institute for Marine and Antarctic Studies, took this photo of a Maugean skate: –
It has featured in newspapers and scientific papers such as “Movement, habitat utilisation and population status of the endangered Maugean skate and implications for fishing and aquaculture operations in Macquarie Harbour” by Justin Bell, Jeremy Lyle, Jayson Semmens, Cynthia Awruch, David Moreno, Suzie Currie, Andrea Morash, Jeff Ross and Neville Barrett.
Further in “Our submission to the Federal Government on Maugean Skates” in MARINE Life magazine for Autumn 2024, “What went wrong? It is beyond doubt that the current issue in Macquarie Harbour is oxygen levels. Also clear in the studies is that the salmon industry is a big player in creating that adverse environment for the skate, along with other environmental factors like marine heatwaves and environmental river flows.”
There is said to have been a large drop in dissolved oxygen in the middle and southern parts of the harbour in 2016*, but it is said to have improved since then, although likely not enough.
* (About 3200 skate were estimated to live in Macquarie Harbour in 2016.)
“Our submission to the Federal Government on Maugean Skates” in MARINE Life magazine for Autumn 2024 goes on to say, “Physiological experiments demonstrated that adult Maugean Skate are quite capable of surviving chronic exposure to hypoxic conditions (< 20% DO), but in the long-term it seems to do them no good. There is an apparent decline in the number of young skates in the population. This was attributed to “recent changes in the environmental health of the harbour (especially dissolved oxygen levels), coupled with the consequences of climate change (including occurrence of extreme weather events)” may already be challenging the skate’s capacity to cope with the environmental conditions in Macquarie Harbour.”
“While the skates can briefly tolerate warmer surface or saline bottom waters, the species prefers zones around 10 metres deep with dissolved oxygen levels of between 60% and 80%. Fish farming in the harbour has been badly affecting oxygen levels and, while it has been heavily reduced in recent years, over controversies about excess nutrients in the waterway, the problem persists.”
“Other actions
The Maugean skate is also likely to have disappeared from Bathurst Harbour, a pristine wilderness where there is no salmon farming. We need more research money and time to find out what went wrong in more detail.
In the meantime, salmon farming feed inputs need to be significantly reduced if not stopped in this unique and badly flushed waterway. It appears that Macquarie Harbour, while a great farming resource economically, is a not a good spot for fish farming if you want to protect natural values. The current issues with Maugean skates come after a series of problems with nutrients more generally.
The recent Tasmanian Scalefish Review has proposed banning netting in many parts of the harbour. It’s a positive step that Marine Life Network supports, but it will not be enough if oxygen levels are also not managed.
There is also a role for a more finessed environmental flow regime in the basin, particularly during emergencies. It may potentially come at the cost of Hydro generation revenues, but the current response, that nothing can be done, seems unsatisfactory.
A $2.1M Recovery task force was formed, which was immediately criticised for being too salmon industry heavy, with really only one environmental representative. Having seen these recovery groups do some good before, let’s see how they go and hopefully it doesn’t get sidetracked by industry. The insurance population plans are great.
The West Coast Mayor called it a cash splash, putting the livelihood of Tasmanians at risk. The millions spent on the salmon industry response, or their impacts on oxygen levels, were not apparently an issue to be addressed. We have seen the salmon industry move into overdrive to explain away the ongoing media disaster that is their operation in Macquarie Harbour. The pitch has been a lazy one, that we can have everything, including plenty of Macquarie Harbour fish farming.
While a technological solution is psychologically enticing, we should avoid thinking that there are only easy solutions. Man-made oxygen pumps have been used in mountain lakes previously. They were reportedly a success in WA (but appear to have stopped being used there). However, unlike the Swan River, Macquarie Harbour is the size of some European countries. It seems like a mammoth and expensive undertaking ($6M of Commonwealth money over two years just for the pilot). We suspect the main benefit is likely to be for salmon production. It would be a perverse outcome if the only benefit was a localised and publicly funded dissolved oxygen improvement around fish farms, with little broadscale benefit for Maugean skates. However, we should keep an open mind at this stage.
“The economic dilemma
The entire Tasmanian 2018/19 direct value (GVA) for aquaculture was $230M, with $650M total economic benefit, and Macquarie Harbour is only part of this total. The Macquarie Harbour EPA maximum permissible biomass is 9500 tonnes. Bartelys give a wholesale smoked salmon spot price of $5000 per tonne to the producer. That’s $47.5M gross sales, profit is way less, not all of that figure is spend on the West Coast.
The fish farming industry does not appear to be a major employer of West Coast residents, although in this economically depressed area all jobs are important. Previous complaints from the West Coast Council have been that the jobs are largely taken by people in the North West who commute to work daily, not by local residents. The West Coast Council failed in a bid to charge rates on fish farms, so the community funding benefit to the West Coast has been limited.
While there are some economic impacts, it might be time to rethink the stocking levels in Macquarie Harbour, and we may need to accept that industry expansion in this harbour has failed. Even at a reduced stocking level of 9500 tonnes it appears that the industry can’t achieve what should be the minimum environmental requirements for an industry of this kind.
The Australian Government has said it aimed to have measures in place by 2027 for “an improved trajectory” by 2032. It sounds like that’s going to be too little too late.
“There’s lots of evidence to say that the population is in very serious decline,” Dr Neville Barrett said. “I personally predict it’s likely to be extinct within a decade on the current trajectory.” Associate Professor Jayson Semmens, the head of the skate research program at IMAS backed up those comments, “We have seen mortality events, and they are sudden and impossible to predict … They have the potential to remove … a large proportion of animals,” he said.
“Conclusion
We can’t commit a unique creature to extinction, we understand the dilemma, but our members are not ready to assign something so special to memory, or a jar of formaldehyde in a museum. The Premier said that skate and salmon had to coexist, but that may well be logically impossible? Skate cannot learn how to live without oxygen. We are the ones that will need to adapt our plans, business as usual won’t be enough. We have the smarts and the resources to save the Maugean skate, it’s the will we lack. We trip up as soon as everyone hints at an economic cost, regardless of how modest that might be. A mistake in this space is forever. We suggest:
- More scientific research, and ongoing monitoring which means funding for bodies like IMAS.
- A suspension of fish farming activity in the harbour as soon as that can be rationally organised, and not over a period of years.
- A recovery plan, formulated predominantly by scientists rather than the multitude of industry bodies currently engaged in the plan.
- The State Government should also advance its plans for netting bans in Macquarie Harbour.
Apologies to Joni Mitchell, but “they took all of the fish and put them in a fish museum and charged the people dollars just to see them.
(Header photo taken by Dr Neville Barrett.)