Solent Seascape Project takes huge step forward to bring oysters back to the River Hamble

Foundations for the largest restoration reef in the Solent have been laid this week, as part of the Solent Seascape Project – a multi-million pound initiative to restore marine habitats across the Solent region.

This five-year partnership, involving the University of Portsmouth and funded by the Endangered Landscapes Project, aims to restore a wealth of diverse marine species and habitats back to the Solent. 

Working closely with the River Hamble Harbour Authority and local contractors Jenkins Marine,  ocean conservation charity Blue Marine Foundation laid a thin veneer of shingle mixed with cockleshells, known as ‘cultch,’ covering 2,500 metres square onto the seabed.

Oysters sourced from south Wales will be transferred to the site to seed the area at the Swanwick bend in the River Hamble in a few weeks, after passing through a strict biosecurity process where they are cleaned, measured and checked.

The Solent was once the largest and most important oyster fishery in Europe, but over the last decade oysters have significantly dwindled in numbers as a result of poor water quality, competition from invasive species, disease and fishing pressure.  The loss of the native European oyster not only negatively impacts the livelihoods of local fishermen, but also removes the many ecosystem services that a healthy oyster population provides.  Adult oysters can filter as much as 200 litres of seawater each day, improving water clarity and removing excess nutrients.  Oysters also stabilise marine sediments and dramatically increase biodiversity, including commercially important fish species.

Dr Joanne Preston, Reader in Marine Ecology and Evolution at the University of Portsmouth, said: “This reef deployment is another significant step forward in re-creating the subtidal oyster reef habitat that has been all but lost in the Solent and across Europe.  We hope this reef creates a tipping point; kick-starting a population of native oysters that builds over several generations and provides offspring that will spill over and populate other areas.  We also predict strong biodiversity gains and water quality improvements, which we will be monitoring over the next five years.”

Louise MacCallum, Solent Project Manager for Blue Marine, said: “This new restoration reef has taken more than a year to plan.  The River Hamble is one of the busiest waterways in the UK.  As well as creating a perfect home for 30,000 oysters, it has also been critically important to ensure that our operations do not affect navigational safety for the many people who enjoy boating and water sports on the river.”

In the coming months and years, scientists from Blue Marine, University of Portsmouth and University of Southampton will monitor the new reef.  Oyster survivorship and biodiversity gains will be measured and compared to another part of the river where no restoration activity is to take place.

Louise said: “This will be our second restored oyster reef in the Solent, the first having been built in Langstone Harbour at the end of 2021.  The Langstone reef has already attracted a wealth of marine fauna including cuttlefish, catsharks and even seahorses.  It is exciting to see what kinds of marine creatures our new reef will attract in the River Hamble.”

In 2021 the Solent Seascape Project team restored a 1,000 square metre oyster reef in Langstone Harbour.  To date, this existing reef and the new reef in the River Hamble are the only restored reefs in the Solent region.

“It’s great to be working with Blue Marine on this ecologically beneficial project. This job is a really interesting new challenge for our team and we look forward to future collaborations,” said Dan Jenkins, Managing Director at Jenkins Marine.

Marine habitat restoration is in its infancy in the UK. As well as restoring oyster habitats, the Solent Seascape Project team will be restoring seagrass meadows, seabird nesting habitat and salt marsh across the Solent region. As the project progresses, the team hopes to use the lessons learned to create a blueprint for restoring temperate marine habitats elsewhere in the UK, and beyond.