The Pacific oyster is taking over Europe’s seas. Many have branded it as an invasive pest but bio-businesses old and new are valorising wild stock. We make a case for the Pacific oyster as a potential node in the circular blue economy.
Once a cheap staple, the oyster became a luxury delicacy over the last century. Now, the bivalve is back as a future green food. They act as natural water filters, sequester carbon, and offer nurseries for other marine animals, including fished species. An EU Parliament 2022 Draft Report on sustainable and competitive EU aquaculture stated that oyster companies could be vital in building a sustainable blue economy.
Any efforts to ramp up European oyster production are likely to centre around one species: the Pacific oyster or Crassostrea gigas. This species first arrived in Europe in the 16th or 17th centuries as accidental stowaways on Portuguese ships returning from Southeast Asia. From there, they were introduced to France in the 1860s. Although not a native species, they have dominated European aquaculture for over a century. 98, 681 tonnes were produced in the EU in 201, far outstripping the native European oyster (Ostrea edulis), whose exploitation decreased by around 60 percent between 2007 and 2017. In the UK, the native species have declined by 95% since the mid-19th century – a trend replicated elsewhere.
However, the popularity of the Pacific oyster is causing concern among some groups. Parts of the southern English coast are seeing hundreds of thousands of shells appear almost overnight. With a vigorous reproductive cycle and jagged shells that lacerate the feet of beach walkers, they are becoming the nemesis of tourist boards from England to Sweden. Mountainous oyster beds also pose navigation threats to boats. Cultivating them is already banned in Sweden while regulatory clampdown on Pacific oyster farming threatens UK producers.
There are two types of bio-businesses that rely on the Pacific oyster. First are the established industries that grow them for the food market. Then there are newer companies working with other modes of valorisation. These include biomaterials and condiments derived from the shell or meat, as well as a burgeoning Pacific oyster tourism industry in Denmark and Sweden. We start with UK oyster producers who supply the food market and their concerns that looming conservation legislation may threaten the industry.
Pacific oysters in the UK
If you buy an oyster in the UK, chances are that you are getting the Pacific oyster. Under UK law, the animal is classified as a non-native invasive species and although they remain legal to cultivate, this might soon change. The government’s official conservation advisory group is pushing to ban Pacific oyster farming altogether. They say the Pacific oyster is disrupting wild habitats and outcompeting the native European flat oyster. There are mounting efforts to restore historic European flat oyster populations, most notably in the Solent strait of the English Channel.
UK producers are angered by a possible ban on their prized crop. Gordon Turnbull from Isle of Mull Oysters in Argyll, Scotland commented on the animus against the Pacific oyster: “It frustrates me. Thankfully it’s not an issue north of the border. They serve the same ecosystem functions and benefits as natives only they are more effective for aquaculture, support jobs, and can be eaten all year”. He also says that the Pacific oyster simply ‘tastes better’. Rather than native oyster restoration projects, he believes that the government should be supporting the existing industry that contributes to food supply and much-needed rural jobs.
At the other end of the country in Essex, Maldon Oysters has been commercially cultivating Pacific oysters since 1960. Chris Hadfield, a farmer for Maldon Oysters, told Bio Market Insights that while an outright ban on farming them is unrealistic at this stage, the government is pushing other unhelpful measures. Last year at a Shellfish Association meeting, government officials insisted that Pacific oysters should be labelled in supermarkets as an invasive species.
Chris is concerned that this stigma around the Pacific oyster will discourage younger entrepreneurs from entering and expanding the industry. This would be a huge missed opportunity for the UK, he says, pointing to the oyster’s immense environmental and social benefits. Maldon Oyster’s eight to twelve workers all reside in the local area and as Maldon Oysters expands to meet market demand, it also spends on contractors for support services. They recently invested in a £1 million depuration facility, a site for purifying oysters of contaminants. He also draws attention to their value in carbon sequestration- something the Pacific oyster does just as well as the native species.
Chris expresses bemusement at stories of conservation groups scouring English coastlines with hammers to destroy Pacific oyster beds. He says he and many others in the industry would leap on the chance to harvest wild populations. It appears that the government’s hostility towards the foreign oyster is leading them to overlook small to medium-size producers as potential partners in economically viable conservation.
How Pacific oysters conquered Europe
The story of how the globe-trotting Pacific oyster colonised Europe is itself a cautionary tale about the consequences of long-term environmental mismanagement. In 1890, the British government deliberately imported a live batch from France for an English oyster farm. At that time, the once-booming British wild-catch oyster industry was on the verge of collapse. Stocks of European flat oyster had been decimated by overexploitation and pollution. Oyster catchers were increasingly turning to cultivation, pinning their hopes on the Asian import.
Several decades later, the farmed Pacific oysters in Britain were themselves on the brink. Afflicted by pests from North American stock, coastal pollution, and severe winters, it seemed the Asian species would go the way of the native oyster. In 1965, the British government stepped in with a systematic breeding programme to revive farmed stock. The Pacific oyster’s conquest of the European oyster industry began in earnest as producers found that the Asian species was much easier to grow than its European cousins. While native oysters take 4-5 years to grow big enough to sell, Pacific oysters take only 2 or 3. Rearing Pacific oysters was also cheaper since native oysters require very specific conditions to spawn. These are the reasons why it remains so popular among cultivators today.
Yet the resilient Pacific oyster soon became a victim of its own success. As they filled aquaculture farms across Europe, escapes became inevitable. In the 1900s, British seas were too cold for fugitive crustaceans to survive. When sea temperatures rose over the 20th century, escapees began colonising coasts around England, Wales, and beyond. By the 1990s, they reached Denmark where there are now vast Pacific oyster banks in the Wadden Sea. From there, populations spread North to Sweden and Norway.
Sweden has already banned Pacific oyster cultivation but the measure does nothing to stem growing wild populations. Now, researchers are exploring how bio-businesses could help. The Swedish Environmental Research Institute’s Dynamo project has received million kroner to evaluate sustainable management strategies for the Pacific oyster. It is reaching out to commercial enterprises interested in utilising the shellfish for their products.
Scandinavian oyster production is ripe for growth. Currently, Sweden and Norway import much of their stock. This is despite near-perfect cultivation conditions and the wild Pacific oysters spreading around their coasts. In Sweden, one obstacle to larger-scale commercial exploitation is that shellfish can only be sold for human consumption if they are harvested from coastal areas set aside for agricultural production. Åsa Strand, a researcher on the Dynamo project, says she is exploring how wild oysters found outside agricultural zones might be exploited for non-food products. “We’re thinking about animal feed for fish or for chickens and also for the pet markets.”
Some Swedish companies are already looking beyond culinary uses. Studio Demos is a Stockholm-based interior architecture company founded in 2020 by Elisa Hedin and Frida McDavitt Wallin. In collaboration with the Dynamo project, they are experimenting with the Pacific oyster shell as a sustainable design and architecture material. Seashells have been used the world over in construction, but Studio Demos are one of the few working specifically with the Pacific oyster. Elisa told us how she waits late nights at restaurants to snap up shells from kitchens.
Studio Demos explained their methods: “When fired at high temperatures, burning the oyster shells instead of limestone, we can create quicklime. This quicklime is then mixed with water, sand, ash, and broken oyster shells as aggregate to create concrete. The next step is to build a kiln to start processing the material.” Their challenge is to formulate a recipe that makes a resilient product from the relatively soft shells of the Pacific oyster. Their interest in using the invasive oyster is driven by a belief in degrowth strategies. “We need to completely rethink and upturn how we use the Earth’s natural resources. Even at this small scale that we are currently working in, new sustainable materials can be a starting point for a bigger change. If our project can give insight into how a material can be part of a bigger cycle of reuse, it can hopefully later be adapted to a bigger process.”
Across Scandinavia, wild Pacific oysters afford an easy way for small businesses to diversify their portfolios. Åsa Hardin runs the oyster company Kalvö Ostron in Bohuslän, on the West coast of Sweden. Her family has owned a natural oyster bank here since the 17th century. Around ten years ago, the Pacific oyster arrived on the bank and now co-exist with the native European species. As well as managing the seabed and selling their crop, the company offers oyster safaris. Visitors can pick oysters in their wild habitats and eat them back at the boathouse. A similar model exists in Denmark where tourists are invited to pick oysters for personal consumption in the UNESCO World Heritage landscape of the Wadden Sea.
In Norway, wild commercial harvests of Pacific oysters remain at a small scale but some companies have been making agricultural fertiliser from the shells. Prices for phosphorus, which can be found in the shell and meat of the oyster, have been on an upward trajectory since the 1970s. With concerns over the accessibility of global reserves, demand for readily available local sources of this vital mineral is only set to rise.
A major obstacle to encouraging a new bio-industry around wild Pacific oysters is the stigma that surrounds the species. The native European oysters have a sentimental hold over the collective imagination, partly because people generally equate native species with ecosystem health. By conferring the Pacific oyster with new cultural value, consumers and businesses could be encouraged to see them in a new light. Stockholm design company Studio Demos is making progress on this front. They say that their research on shell biomaterials is also a way of educating the public on the species and eventually plan to present their findings in an exhibition. Activities like this can open more balanced assessments of the Pacific oyster. While often presented as an environmental scourge, it could equally be seen as a potential node in the circular blue economy.
Commercialisation, not eradication
As non-native introductions go, the ecological impacts of the Pacific oyster have been relatively benign. This is especially compared to the human factors that first led to their introduction: the unrestrained fishing that destroyed native stock right up to the rising temperatures now aiding their spread.
Contrary to what some conservationists claim, the Pacific oyster’s effects on native habitats are highly dependent on locality. Some studies show that species can increase diversity in a habitat while others claim there is simply no evidence for Pacific oysters totally displacing any species in Europe. Added to the fact that wild populations are already too large to eliminate, integrating them into a value-adding supply chain makes more economic sense than culling or outright farming bans.
Although wild Pacific oysters are an opportunity for bio-businesses, this does not mean native European oyster restoration efforts are futile. There is one argument in favour of sustaining the native species, which is that the European flat oyster appears much more resistant to ocean acidification and warming. In the meantime, however, the Pacific oyster is here to stay. If valorised strategically, this natural surplus can drive new blue circular industries that maintain functioning ecosystems into the future.