Why native oyster restoration is important, and what success will look like.

Marine ecologists are familiar with the concept of shifting baselines. Callum Roberts’ excellent book, The Unnatural History of the Sea, documents the decline of our fisheries, particularly following mechanisation of fishing in the 19th century. Similar declines have also been experienced by some of our shellfisheries, not least the native oyster.

As a result of overfishing, pollution and disease, native oyster populations have been decimated around our coasts, with only relict populations remaining.

Olsen’s 1883 Piscatorial Atlas graphically illustrates the former widespread distribution of the native oyster around our coast (Olsen, 1883)

Native oyster reefs play an important role in marine ecosystems, providing a range of ecosystem service benefits to humans including food, carbon storage and sequestration, and erosion protection, as well as wider biodiversity and cultural benefits. The formerly extensive reefs will have strongly influenced nutrient cycling and bentho-pelagic coupling (transferring particles from the water column to the seabed) at ecosystem scale.

With increasing recognition of the need to restore and enhance marine ecosystems, there is a renewed interest in seeking to restore native oyster populations.

The UK Native Oyster Network is providing a focus for knowledge sharing on restoration efforts, and has recently published a Native Oyster Restoration Handbook.

The handbook provides invaluable guidance on how to progress restoration projects based on practitioners’ experiences. Key success criteria include:

• Establishing clear goals and targets for restoration projects against which progress can be measured;
• Undertaking a robust feasibility study to determine the potential suitability of restoration sites;
• Obtaining adequate baseline knowledge of the biological, ecological and physical characteristics of potential restoration sites;
• Allowing for the necessary investment of time and resources for logistical and licensing requirements of restoration projects;
• Ensuring that biosecurity risk assessment is integrated into restoration practice; and
• Engaging widely with stakeholders to incorporate local ecological knowledge and build social acceptance.

Several initiatives are also underway in the UK, including work undertaken by Blue Marine, Essex Native Oyster Restoration Initiative (ENORI), Dornoch Firth and Natural Resources Wales (NRW).

We are privileged to be working with NRW on their restoration project in the Milford Haven waterway, and have recently placed oysters in various intertidal and subtidal locations. A programme of ongoing monitoring will take place over the next two years to assess survival.

Owing to their particular sensitivity, the restoration of the native oyster is recognised as incredibly challenging. Careful attention to project design and implementation is therefore essential, but if we get it right, there will be significant benefits for marine biodiversity and for future generations.

Prepared by Stephen Hull, Director

^{References
Olsen, O.T. (1883). The piscatorial atlas of the North Sea, English Channel, and St. George's Channels: illustrating the fishing ports, boats, gear, species of fish (how, where, and when caught), and other information concerning fish and fisheries. O.T. Olsen, Grimsby, 50 maps.}

^{Roberts, C. (2007). The Unnatural History of the Sea. Shearwater.}