Jacob Kean-Hammerson
Blue Marine Foundation (BLUE)
The Solent Oyster Restoration Project is a collaborative project, led by the Blue Marine Foundation (BLUE), that is working to restore oyster populations to England’s south coast through a combination of innovative restoration techniques (https://www.bluemarinefoundation.com/projects/solent/). The long-term vision is to see a healthy, self-sustaining oyster population contributing to improved biodiversity and water quality and benefitting the local community.
The study site
The Solent, a 20-mile strait that separates mainland England from the Isle of Wight, once had the largest native oyster - European flat oyster (Ostrea edulis) fishery in Europe. In 1978, 450 vessels were involved in oyster fishing and 15 million oysters were harvested in that year alone. However, since this peak, the oyster population has declined significantly and in 2013 the fishery collapsed. Today, the entire native oyster fishery remains closed with oyster numbers alarmingly low. The area also faces several other challenges such as pollution and introduction of invasive species that are threatening local biodiversity.
Figure 1. A fully grown native oyster.
Why is oyster restoration important?
Oyster restoration provides a great opportunity to address a number of the issues facing the Solent. Oysters feed by filtering the water and a single adult can process up to 200-liters of water every day. Large populations of oyster can contribute to improved water quality and clarity by removing suspended sediments and pollutants preventing toxic algal blooms and reducing the impacts of nitrates. Increasing the denitrifying potential of the Solent’s habitats could be a remedy to the severely eutrophic waters off the Hampshire coast. Oyster reef habitats across the world are known to be highly productive ecosystems. When left undisturbed they create three-dimensional ecosystems that act as nursery grounds and a refuge for many species, boosting both finfish and shellfish stocks.
Figure 2. Broodstock cages ready to be deployed beneth mariana pontoons.
What has been done?
The Solent Oyster Restoration Project has been operating since 2015 and has employed a number of restoration techniques to bolster local populations. Working with the University of Portsmouth, the project has developed novel restoration aquaculture cages. These cages are designed to keep oysters at high density, so they breed and pump out larvae into the Solent. MDL Marina group have partnered with BLUE on this initiative and have suspended cages from pontoons at eight of their marinas. Since the project started, 23,000 oysters have been restored in these cages. These have been a success, with over one billion larvae being released in a single year. The oyster cages have also attracted a wealth of biodiversity, with over 100 species inhabiting the cages or on the oysters themselves.
Figure 3. Oysters housed in innovative microreefs.
The larvae from these cages settle on the seabed, where BLUE has been running small scale restoration trials. A total of 45,000 oysters reared on oyster farms have been re-seeded over 2 acres of protected seabed. Pilot studies have been testing the ideal density and location of restoration and results have been encouraging, with oyster survival higher than expected. Plans to scale up restoration in 2020 are underway. In order to facilitate large-scale restoration, BLUE and the University of Portsmouth are working together to set up the UK’s first restoration native oyster hatchery. If successful, the hatchery will produce millions of ‘spat-on-shell’ native oysters, which will be reseeded directly from the hatchery to restoration sites.
The partnership
Our partners include the University of Portsmouth, University of Southampton, MDL Marinas, Southern Inshore Fisheries and Conservation Authority, 1851 Trust, and the Hampshire and Isle of Wight Wildlife Trust.
Other projects supported by the Blue Marine Foundation (BLUE)
Outside of the Solent, BLUE work with the Essex Native Oyster Restoration Initiative (ENORI), where significant strides have been taken in the restoration of these historic oyster beds (see MERCES Newsletter No 2). Over 300 cubic meters of shell and aggregates, also known as ‘cultch’, has been laid to promote oyster settlement, covering of 1200m2of seabed. This is now being monitored for oyster recruitment, growth and survival.
BLUE is also working to restore other important marine habitats. In Sussex, BLUE is working with partners including the local Wildlife Trust to pioneer the UK’s first Kelp restoration project. This project has been encouraged by the recent vote by the Sussex IFCA to remove trawling from 302 km2 of their district. The bylaw will now go to the Environment Secretary for approval.
Figure 4. School students learn about the benefits of oysters.
To keep up with developments of the Solent Oyster Restoration Project visit https://www.bluemarinefoundation.com/projects/solent/ or follow them on social media (Twitter: @SolentNative, Instagram: @SolentOyster). Jacob Kean-Hammerson (jacob@bluemarinefoundation.com).
