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Royal Navy helps oysters return to Solent after four decades
29 August 2024
The Royal Navy is helping to reintroduce oysters to the Solent after nearly half a century thanks to a unique project opposite Portsmouth Naval Base.
Some 2,000 European flat oysters – once prevalent in waters between Hampshire and the Isle of Wight – are being grown with the goal of releasing them into the Solent as part of a wider project by a maritime charity to re-establish the population, clean the sea and enhance local marine biodiversity.
At a cost of £5,000, several crates have been installed on pontoons at the southern end of Whale Island – home to the Royal Navy’s headquarters – for the oysters to grow from infancy to adulthood in waters used daily by cross-Channel ferries, merchant vessels visiting the commercial port, and warships operating from Portsmouth Naval Base.
The project, which contributes to the Blue Marine Foundation’s Solent Oyster Restoration initiative, is managed by Harriet Rushton of DE&S Salvage and Marine Operations (SALMO) Wrecks team, and is funded by the Defence Infrastructure Organisation.
It has already released a batch of 200 European flat oysters (Ostrea edulis) to the River Hamble between Portsmouth and Southampton.
This year the conservationists are raising 2,000 oysters – and hope most will survive the vagaries of the British weather – to join the older cohorts and help breed, spawn and restock Solent waters, as well as filtering them, improving water quality and enhancing biodiversity.
“It has been very exciting to establish and manage this project,” said Harriet.
“These oysters are being grown for conservation, re-introducing a lost native keystone species in the Solent, which will enhance biodiversity and help clean the water.
“This shows the Ministry of Defence’s commitment to improving the UK’s ecosystem and helping to address climate change, thus contributing to minimising climate and ecosystem pressures on MOD training and operations.”
This is a long-term project – it may well be a decade or more before the team’s efforts bear fruit – but Rod Jones, the Royal Navy’s Senior Maritime Environmental Protection Adviser, believes if successful there is potential for the initiative far beyond the Solent.
“If we can grow oysters here – which is far from an ideal environment as a very industrial setting – then there are clearly opportunities to grow them elsewhere, other naval bases or MOD sites,” he added.
“The Navy has been operating in the Solent for centuries so it is only right that we should be involved in protecting its environment.”
Every couple of weeks, he, Harriet and the Whale Island Conservation Volunteers inspect the oysters and their crates as these can become fouled with algae, sea squirts and other marine organisms, especially during spring and summer, impacting the oysters’ ability to feed and grow. It takes up to 18 months for the oysters to reach adulthood.
The Navy has been operating in the Solent for centuries so it is only right that we should be involved in protecting its environment
The Solent was once home to the largest fishery of European flat oyster, in Europe, but since the peak in the mid-19thCentury, numbers have dropped by 95 per cent as a result of overfishing and pollution and their niche is now occupied by the invasive Pacific oyster, Magallana gigas. By the 1980s, numbers of the native species were negligible.
Reintroducing Ostrea edulis to the Solent has widespread benefits for the local environment.
A single adult oyster – measuring just 8-9cms – can filter up to 200 litres of water a day, removing chemicals and pollutants, improving not just the clarity and quality of the sea, but allowing sunlight to penetrate further, enabling species and habitats dependent on the sun’s rays, such as seagrass and saltmarsh, to grow.
Cleaning the waters around Whale Island will benefit Royal Navy personnel and Sea Cadets. They are used by divers and sail training and, in summer, leisure and adventurous training activities.
Once released, and settled in the Solent – Blue Marine Foundation has established artificial reefs in Langstone Harbour (between Portsmouth and Hayling Island) and the River Hamble (between Southampton and Fareham) – the oyster shells merge into one another to form reefs which become biodiversity hotspots, providing shelter and food for marine life, from tiny plankton to larger fish species. In this way, they are classed as a keystone species.
Oysters also remove carbon from the environment, extracting carbon ions from seawater to build their shells. When they die, their shells become buried beneath sediments, eventually transforming into solid beds of limestone, effectively removing carbon from the atmosphere.
“It is great to be working on this project together to reintroduce native oysters to the Solent,” said Dr Luke Helmer, restoration scientific officer at Blue Marine Foundation.
“As part of this, we have created artificial reefs, made from shell and gravel material, onto which the oysters are released, as they require hard substrate on which to attach, grow and spawn.
“They can then create their own reefs and further enhance the health of the local marine environment. It will be a pleasure to see this collaboration in a conservation project continue to unfold.”