During the 2019 black summer bushfires, oyster farmer Kevin McAsh’s leases along the Clyde River on the New South Wales south coast were badly charred. Afterward, floods washed debris upstream into the Batemans Bay estuaries.
“The elders said they’ve never seen anything like it. All the ground cover was destroyed,” he says.
“The soil was scorched. Now there’s nothing left to hold it. Mangroves with their feet in water were cindered.”
Batemans Bay oyster farmer Kevin McAsh has joined calls to future-proof the region’s aquaculture industry.
Although it will be years before the mangroves that McAsh is replanting can restabilize the riverbank, he is grateful for the ongoing work of scientists monitoring the water quality.
Oyster leases can generate $40,000 a hectare in an industry the state government calls the most viable aquaculture sector in NSW.
Yet with scientists estimating that Australia’s east coast estuaries are warming four times faster than anywhere else, McAsh has joined the call to future-proof the region’s blue economy.
Kelp forests stripped
Prof Maria Byrne from the Sydney Institute of Marine Science says south coast marine ecosystems are undergoing “a dynamic state of change due to climate warming, freshwater runoff, and storms”.
Up to 50% of south coast shallow rocky reefs now appear as urchin barrens in aerial surveys, where bare rock crawls with native sea urchins that have stripped kelp forests.
At a 2021 symposium in Narooma, researchers, marine industries, and citizen scientists they formed the view that natural urchin predators – blue groper, snapper, and lobster – can no longer control the urchins that have destroyed local abalone breeding habitats.
After 25 years of diving for abalone at Tomakin, sea urchin processors Chris and Rachael Theodore have pivoted into an emerging market that addresses the urchin plague by harvesting its roe. This delicacy is in demand internationally.
But with roe produced during the breeding cycle only, kelp forests that filter the water flowing into estuaries need more rigorous urchin suppression.
The geoscience videographer David Rowland says part of the problem is the urchin’s capacity to remain dormant for 50 years.
Rowland’s remotely operated underwater vehicles have filmed blue groper grazing on urchins.
“As soon as kelp regrows, the cycle starts all over again. It will take industrial-scale solutions to remove them,” he says.
Although blue groper is not registered as a threatened species, it is one of the few fish that can graze sea urchins. Photograph: Jen Thompson
A Department of Primary Industries (DPI) spokesperson told Guardian Australia that future measures “may include targeted removal of purple sea urchins under controlled conditions”. However, political responses to coastal ecosystem health on the south coast have been mixed.
Just before black summer, while Australia prepared to join 72 nations in protecting 30% of the world’s oceans, the Berejiklian government opened five areas within the Batemans marine park to recreational fishing, declaring an amnesty for fishers.
The move was announced by the former Bega MP Andrew Constance, who said at the time: “Tragically, a lot of these areas weren’t locked up for any sound ecological reason, meaning recreational fishers missed out simply because of senseless politics.”
Some of the Nature Coast Marine Group (NCMG) members told Guardian Australia they contacted Constance about their concerns, inviting him to swim out onto the reefs with fishers, traditional owners, and businesses from his electorate.
The scientist and NCMG president, Dr. Jane Elek, says no response was received.
Although blue groper is not registered as a threatened species, it is one of the few fish that can graze sea urchins, Elek says.
They need protection because the species “are all female until one matures and becomes a male with a harem of females. If that male gets caught, they can’t breed.”
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Research in Tasmania shows overfishing of natural urchin predators in the state’s waters has destroyed the kelp canopy that regulates ocean acidity and removes carbon from the atmosphere.
The state treasurer and former environment minister, Matt Kean, answered “yes” when asked in late 2020 whether he intended to restore the sanctuary zones.
But he added that a final decision could not be made until a review of no-take zones was completed. “Let’s listen to the science, let’s listen to the experts, a’s make policy in line with that advice,” he said.
By December 2021, Kean had moved on from the environment portfolio, and Constance had announced his resignation from state parliament to run for the federal seat of Gilmore in the 2022 federal election, a bid he lost.
Healthy kelp at Batemans marine park. Photograph: Elizabeth Walton
The fast-tracked consultation process Constance had previously announced in 2019 was still underway in January 2022.
“We can only hope these issues are addressed in the state election,” says the independent MLC Justin Field, who sees no scientific basis for fishing in sanctuaries.
The new state member for Bega, an amateur oyster farm, Michael Hollander, says “climate change is the number one issue”.
“You either have a marine park, or you don’t, but we need to consult people – the Indigenous owners, the recreational and professional fishermen – we also need to hear about the correct zones from scientists.”
Scientists, local businesspeople, and Nature Coast Marine Group members paddle out to inspect Batemans marine park.
The federal member for Eden-Monaro, Kristy McBain, says the region is rightly proud of its aquaculture.
“I am committed to seeing the sector’s continued viability,” she told Guardian Australia.
The new minister for regional development, local government, and territories, McBain, says the restoration of shellfish reefs lost Australia-wide, including those in Narooma, will help draw more visitors supporting the ecotourism, hospitality, and fishing sectors.
“I will work hard to make sure we get the balance right between caring for our marine environment and generating economic activity in our region,” she says.
Constance was approached for comment.
Restorative ocean farming
The marine biologist Jo Lane is concerned that the lush kelp forests she once saw when diving every day off the coast of Narooma are now bare.
With the right investment, she says her breakthrough work growing kelp in the laboratory offers a carbon-negative contribution to an emerging blue economy.
Marine biologist Jo Lane is concerned that the lush forests she once saw when diving for kelp daily are bare. Photograph: Elizabeth Walton
“Kelphotosynthesizeses and restorative ocean farming improve oceans while it grows sustainable produce,” she says.
“Acidification is damaging crustaceans and mollusks, impacting the food chain globally.”
A collaboration between The Nature Conservancy (TNC), Eurobodalla shire council, and the federal government plans to restore native shellfish to the Narooma foreshore.
Kirk Dahle, a TNC spokesperson, says the planned new oyster reefs will purify the estuary.
“They don’t contribute to an oyster farmer’s income, but they improve their paddock,” he says.
According to McAsh, “it all goes together”.
“Estuary health, kelp, and marine parks – what we need is more science to gather baseline data, then we’ll have a new day when we can start to plan for industries that will take us into the future.”