Native Oysters

Native oyster reefs were once abundant in European seas, but, sadly, it is estimated that populations have declined by 95% since the 19th century. Now, native oyster reefs are one of the most threatened habitats in Europe.

The key driver behind this huge decline is historic overfishing; however, habitat loss, disease, pollution, and invasive non-native species are all contributors. Native oysters are also characterised by a slow growth rate and sporadic recruitment, which further limits their success.

In Northern Ireland, extensive oyster beds are known to have existed in Carlingford Lough, Lough Foyle, and Belfast Lough for several hundred years, but most stocks crashed during the late 19th or early 20th century. Now, only a small wild population exists in Strangford Lough and, in the summer of 2020, live native oysters were discovered for the first time in over 100 years in Belfast Lough – evidence that the environmental conditions for re-establishment were right. 

The native oyster is a Priority Species in the UK and Northern Ireland. A Priority Species requires conservation action because of their decline, rarity and importance in an all-Ireland and UK context. It is included in the OSPAR List of Threatened and/or Declining Species and Habitats for the North-East Atlantic.

Native oysters are ecosystem engineers. When oysters grow together, they form reefs that create habitat for fish, crabs, anemones, sea squirts, and many other species. A single oyster can filter large quantities of seawater each day, helping improve water clarity and water quality. Healthier water can benefit other important habitats such as seagrass and saltmarsh. 

Ulster Wildlife is leading efforts to restore the European native oyster in Northern Ireland's waters and rebuild one of Europe's most threatened marine habitats, alongside volunteers, communities, researchers, and partners. 

Native oyster nurseries 

Since establishing Northern Ireland’s first native oyster nursery in 2022 at Bangor Marina, we have established a network of nurseries in Belfast Harbour, Carrickfergus, and Glenarm Marina. Together, they support over 3,000 adult oysters and produce millions of larvae every year to help restore this once-abundant species. 

Native oyster nurseries are cages suspended beneath marina pontoons, providing a safe place for adult oysters to grow and breed. The oysters release millions of tiny larvae into the water, helping new oyster populations develop naturally. Our amazing volunteers help care for the oysters, monitor their progress, and play a vital role in bringing back this lost habitat. 

Our work goes beyond oyster nurseries. Across Belfast Lough, Larne Lough, and Carlingford Lough, we are carrying out coastal and underwater surveys to look for native oysters and identify suitable seabed habitats for restoration. Gathering baseline information helps us understand current conditions and measure the success of future restoration efforts. 

Scaling up restoration  

Our long-term vision is to help establish thriving oyster reefs at sea that can grow, reproduce, and support healthier seas for generations to come. 

In 2026, we took an important step towards that goal with our first seabed deployment in Belfast Lough. Working with partners, we deployed 2,000 adult native oysters and 30,000 juvenile oysters onto the seabed. This marks a significant milestone for oyster restoration in Northern Ireland and represents the transition from nursery-based conservation towards active reef restoration.

We also launched our first floating oyster reef, or ecosystem pontoon, at Glenarm Marina. This innovative approach creates a much larger nursery beneath the pontoon, acting like a giant underwater cage that can safely accommodate far more oysters. By increasing the number of adult oysters available, it has the potential to support future restoration efforts. The project is also helping us learn more about the wildlife that benefits from oyster habitats using underwater cameras and automated species detection technology. 

We are incredibly grateful to our funders DAERA and Wilson Resources, alongside our partners Belfast Harbour, Ards and North Down Borough Council, and Mid and East Antrim Borough Council for supporting this pioneering oyster restoration work. 

Choose sustainable seafood options

Many of the oysters on sale and eaten in the UK and Ireland today are Pacific oysters. This is an invasive species, and was brought here intentionally from Japan in the 1970’s following the demise of our native oysters. Many farmed Pacific oysters are "triploid" - meaning they are sterile and won't impact on wild populations. It's not entirely failsafe - but they are a more sustainable option. 

Join Ulster Wildlife and together we can BRING NATURE BACK