Climate disasters mean oysters could be in short supply this Christmas

Oysters will be scarcer, smaller and more expensive on Christmas tables this year after twin climate disasters in two states – floods that devastated northern NSW leases and the algal bloom that contaminated crops in South Australia.

The disastrous season comes amid a nationwide effort to restore wild native oyster reefs in sites such as Melbourne’s Port Phillip Bay and the Noosa River on the Sunshine Coast, as scientists are belatedly recognising their water filtration role as “the kidneys of the coastline”, as well as their leases’ role as a breeding ground for fish and as a buffer for coastal storm surges.

Oyster farmers face the cascading effects of climate change on food production described in last week’s National Climate Risk Assessment, but they are also grappling with a lack of understanding from the public and governments.

In one example, a NSW oyster farmer from the Mid North Coast was initially asked to count dead oysters to claim disaster grant money – an impossible task when the oysters numbered in their millions and many had been washed out to sea.

Brandon Armstrong, owner of Armstrong Oysters in Laurieton near Port Macquarie and chair of the oyster committee for NSW Farmers, said the May floods affected oyster leases in estuaries north of Sydney to the Queensland border, especially from the Manning to the Nambucca River.

“The biggest problem is we’ve only just had the 2021 and 2022 floods, so we’ve been rebuilding from that,” Armstrong said.

“It’s been a challenge because oysters take three years to grow; so we were only just seeing the crop that was hatched after the last floods coming to maturity in time for the 2025 summer season.”

When the floods came, Armstrong spent all day rescuing neighbours and their animals and ferrying them to safety in his boat, stopping only when darkness fell and it became too dangerous. The same treacherous waters were washing away his livelihood for the third time in five years.

At his lease on the Camden Haven River, Armstrong lost about 11 million Sydney rock oysters, either killed in place from dirty floodwater or washed out to sea. Others recovered, but they have grown more slowly because of the ordeal.

Jonathan Ford from Bells Island Oysters, on Wallis Lake in the Forster-Tuncurry region north of Newcastle, lost almost four million Sydney rock oysters, about half his stock for the next three seasons.

The NSW government estimates that about a quarter of the state’s farmed oysters, which also include South Coast crops, are sold interstate.

The oyster shortage will also be compounded by the Karenia mikimotoi algal bloom in South Australia that has been choking about a third of the state’s coastline for months, killing animals including cuttlefish and dolphins.

Dr Dominic McAfee from Adelaide University said many oyster farmers in South Australia were unable to sell their product because they were contaminated by brevetoxins from feeding on the algae.

‘Unsung ecological superheroes’

Before European settlement, shellfish reefs covered hundreds of thousands of square kilometres of coastal waters around Australia, McAfee said. Most were wiped out in colonial Australia by dredging the reefs both to eat the oysters and to grind their shells for cement (as a substitute for lime), and later by run-off.

“Oysters are unsung ecological superheroes,” McAfee said. “They provide complex habitat, which supports really high density biodiversity. Lots of fish breed on oyster reefs, and the juvenile fish will live on there until they move to offshore habitats.

“They are the kidneys of our coastline because they are really effective at filter-feeding. One oyster can filter 100 to 200 litres of water a day, and the historic reefs would have been made up of billions and billions of oysters. If you scale up the work I did to the historic extent in South Australia, they would have been filtering over half a trillion litres of water a day, and that’s extremely conservative.

“They also can protect shorelines from storm surges, and they can grow faster than sea level can rise.”

Chris Gillies, a marine biologist at Offshore Biotechnologies, said oyster aquaculture provided many of the same benefits as natural oyster reefs.

“Oyster rafts act as fish nurseries, and by filtering the water and improving light conditions, oysters benefit other important ecosystems like seagrasses,” Gillies said.

However, McAfee said many commercial crops were Pacific oysters from East Asia, which are “voracious feeders” and can sometimes outcompete native species.

McAfee is involved in projects to locate where shellfish reefs used to be and restore them in the wild, working with partners such as his university, various state governments and The Nature Conservancy.

After a successful pilot project in 2015, there are now about 60 shellfish reef restoration projects around Australia – dozens in Port Phillip Bay in Victoria alone, but also in Botany Bay, Port Stephens and Myall Lakes in NSW, the Brisbane River and Noosa Estuary in Queensland, and Perth’s Swan-Canning River and Oyster Harbour, Albany in Western Australia.

In South Australia, 35 hectares of boulder reefs at Glenelg in Adelaide have brought back the native flat oyster, which was functionally extinct except for one location in eastern Tasmania.

“Those are large-scale reef restorations, some of the largest in the world, and some of them have been a massive success,” McAfee said.

The good news is that oysters in South Australia have so far not died en masse as a result of the algal bloom, McAfee said. He suggested that since oyster farmers cannot currently sell their stock, they could be given work in restoration since they have the boats and knowledge.

Both the NSW floods and the South Australian algal bloom have been driven at least in part by a marine heatwave encircling the continent, highlighting the vulnerability of the oyster industry in a warming world. Ash from the 2019-20 bushfires also killed oysters.

McAfee said the likelihood of future climate-driven events was a reason to ramp up restoration because oysters increased the resilience of marine ecosystems.

The commercial oyster industry has also been investing in resilience. At Armstrong’s farm, he had already converted half his infrastructure to flood-resistant rafts using grant money from the 2021 floods. These survived the May floods, while his older ones were damaged.

Counting oysters

The biggest problem this year for NSW oyster farmers has been the difficulty obtaining state government relief grant funding in a system designed for land-based agriculture.

“With aquaculture, there’s a miscommunication between what farmers are requesting [and what is understood],” Armstrong said.

“We’re not asking for fodder or asking for hay or asking for fences. We’re asking for oyster spat; we’re asking for posts and rail; we’re asking for baskets. It’s a different terminology.”

NSW Premier Chris Minns and Agriculture and Fisheries Minister Tara Moriarty visited after the floods and oyster farmers pleaded for speedy flood assistance but, Armstrong said, “the help just didn’t come”.

The NSW Rural Assistance Authority offered up to $75,000 in special disaster relief grants, but the requirements to access the money were onerous and many farmers were forced to wait months.

Ford from Bells Island Oysters had his oyster leases inundated by five to six metres of floodwater, and his shed and depot were two metres under as the estuary filled with debris – trees, hay bales, furniture and fridges.

While he was approved for a grant quickly, he was forced to spend the money and claim it back. After he spent the first $11,000 buying new oyster stock, he was then asked to provide “the number of lost oysters including age, grade and size, confirmation of when they were originally purchased, and previous input costs for oysters/spat originally outlaid through a valid tax invoice and proof of payment” before the money would be repaid. He got them to back down but he then faced further hurdles with his next claim.

“It’s not like I’m going to buy a V8 Commodore or lunch down at the local shop,” Ford said. “The grant is to help oyster farmers to get back on their feet. There’s no more legitimate thing to purchase with the money than buying oysters. As it stands, we’re almost spending $90,000 to receive $75,000.”

Moriarty said: “After ministerial intervention a month ago, the processing times for natural disaster funding assistance have been drastically cut with an average processing time now of only 24 days, and 77 per cent of applications have been determined.”

She said the Minns government was investing in the aquaculture industry, including oyster farming, to better manage climate change risks and boost economic growth.

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