Pacific oysters have been cultivated in UK waters since the 1960s, in common with other countries in Europe. However, their spread beyond aquaculture to create wild reefs in sea beds and estuaries makes them an "invasive species", according to the UK Government.
The UK has already imposed tighter controls on the cultivation of Pacific oysters, banning expansion of farming north of latitude 52°, and restricting existing aquaculture south of this line.
The issue has come under renewed focus this week with the news that one of England's largest landowners, the Duchy of Cornwall, intends to "phase out" Pacific oyster cultivation on its lands.
Pacific oysters have been farmed on Duchy lands since 2006. However, the Duchy will no longer renew leases for cultivation after current permits expire. The Duchy's marine conservation team is also operating a clean-up programme to remove wild-seeded Pacific oysters from estuaries and waterways on the estate.
However, the Shellfish Association of Great Britain warns the move will wipe out many shellfish farming businesses, many of which are small operations.
To find out more, We Are Aquaculture spoke with the trade association's chief executive, David Jarrad.
"It's a huge blow to the sector and potentially a threat to the rest of the industry," says Jarrad.
"In two to three years there won't be any oysters being grown in the estuaries of the West Country," he says.
"Other landowners are quite likely to follow suit. So if the Duchy of Lancaster or other individual landowners around the country make the same decision, that's the end of the industry."
But the irony, Jarrad says, is that restricting farming will not solve the problem.
Pacific oysters are broadcast spawners, producing larvae that can travel up to two hundred miles with ocean currents. Jarrad points out there are already significant wild populations of Pacific oysters off the coasts of neighbouring countries like Ireland, France, The Netherlands, and Denmark, as well as wild populations around the UK coast.
"The species is here. Even if you sacrifice the industry, it's not going stop the problem of the wild populations. If that happens, the Pacific oyster populations are just going to explode even more because they won't be being harvested by the very industry that uses them as a resource."
The Pacific oyster was introduced in the UK and other European countries during the 1960s as a solution for the failing native oyster industry, which declined due to a combination of overfishing, pollution, and disease. The pathogens which attack native oysters are still abundant in British waters, Jarrad says, making the native species unsuitable for shellfish farming.
"I'm all in favour of small-scale native oyster restoration programmes. But the perception that native oyster cultivation is going to replace Pacific oyster cultivation is nonsense. It's a fantasy," he says.
Jarrad says that in 2020, UK shellfish farmers produced just over 600 tonnes of Pacific oysters. According to European Commission figures, the EU produced 98,000 tonnes in 2020, with France as the largest producer.
"Pacific oysters are cultivated along the Normandy and Brittany coast, spawning only a matter of thirty miles away when there's a larval drift of two hundred miles. It is bonkers to think we can have any impact on wild populations by stopping small cultivators in the UK," says Jarrad.
In other European countries, Pacific oysters are no longer designated an "invasive species" but are considered "naturalised".
"If we accepted them as naturalised and allowed the cultivation to continue, those cultivators would not only have their own projects, but they would also be able to fish the wild stocks and reduce the wild population," Jarrad says.
The Pacific oyster featured in debate at the UK's House of Commons earlier this month. Mark Spencer, UK Minister for Food, Farming and Fisheries, admitted "The Pacific oyster is an important species for the shellfish aquaculture industry in England." However, he said their status as an invasive species means tight controls are necessary.
Currently, DEFRA, the UK's Department for Environment, Food and Rural Affairs, does not permit expansion of Pacific oyster farming north of latitute 52°. South of this latitute, the government will consider new applications and existing farms on a case-by-case basis. This will also take into account the impact on Marine Protected Areas, the minister said.
"Evidence from Natural England suggests that they can alter habitats and ecosystems through reef formation, which can displace native oysters and have a negative impact on native biodiversity," Spencer said.
However, he added, "I am keen to understand more about their impacts and benefits, and possible mitigations. As such, I will seek to meet with officials, regulators and scientists in the coming weeks to explore the matter further."
Meanwhile, shellfish industry stakeholders remain worried, but cautiously hopeful of a way forward.
"I always think there's a possibility and opportunity. Common sense has to prevail on some level," says Jarrad.
"The UK is alone in Europe in gold-plating the same legislation other countries are working under, and taking a completely different interpretation."
"Natural England have themselves said they acknowledge and accept that the species will spread over the next 30 years to all around the UK coast. So why shut down the industry now?"
The Shellfish Association of Great Britain is the UK industry's trade body based at Fishmongers' Hall in London. Its membership is wide-ranging, composed of shellfish farmers, fishermen, fishermen's associations, processors, commercial traders and retail companies including restaurants. Members also include the Inshore Fisheries Conservation Authorities, organisations such as Seafish, academics, scientists, consultants and anyone with a passion for shellfish.
First founded as the Oyster Merchants' and Planters' Association in 1903, and renamed the Shellfish Association of Great Britain in 1969, the association has steadily extended its range of activities from "harvest to sale" in over a century of support to the industry.
