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ESSEX NATIVE OYSTER RESTORATION INITIATIVE

 
 

THE NATIVE OYSTER

has lost 90% of its original range

 
 

RESTORATION

of one of the most threatened habitats in Europe

 
 

COLLABORATION

between oystermen, NGOs, government and academia

ABOUT US

The Essex Native Oyster Restoration Initiative (ENORI) is a collaborate effort between oystermen, government, environmental NGOs and academia.

Together we are working towards the Essex estuaries having self-sustaining populations of native oysters that provide ecosystem services, sustainable fisheries and increased biodiversity whilst recognising their cultural importance.

This is the largest native oyster restoration project in Europe; together we will recover native oysters and native oyster beds in the 284km2 Blackwater, Roach, Crouch and Colne Marine Conservation Zone designated in 2013 for their importance.

ACHIEVEMENTS

Designation of the 284km2 Blackwater, Roach, Crouch and Colne Marine Conservation Zone (MCZ) in 2013 with the conservation objective to recover native oysters and native oyster beds
Creation of a 200ha no-take zone, the Blackwater Conservation Box, specifically for native oyster bed recovery.
Adoption of a fisheries management plan to recover native oyster populations in the MCZ which when resilient enough will allow a sustainable fishery.
The confirmation of the Native Oyster Permit Byelaw in 2018 that protects the fisheries management plan and Blackwater Conservation Box by law.
Secured a marine license for restoration activities, the first of its kind in England.
Translocation of 25,000 mature native oysters in the MCZ to restore a nationally important breeding population.
Established a supply chain of waste oyster shell from stalls in Borough Market, London, and on the Isle of Mersea to relay in the sea and improve the seabed for oysters to settle and grow (another UK first).
Helped establish first UK network for the restoration of native oysters.
We currently have 2 PhD students at the University of Essex, studying the threats that predators for the native oyster, and also of oyster co-management.

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WHY SHOULD WE PROTECT THE NATIVE OYSTER?

Native oysters (Ostrea edulis) are critically important both ecologically and economically.

As well as being an important part of our marine life, the native oyster provides us with many ecosystem services – these are the benefits we receive for free from the natural environment.

BIODIVERSITY

Oyster habitats support a higher biodiversity of invertebrates and fish than surrounding unstructured habitats. Recent research recorded 96 species living on or amongst our native oyster.

SUPPORTING FISH POPULATIONS

Oyster beds provide valuable nursery habitat for many fish species including those of conservation and/or commercial importance.

IMPROVING WATER QUALITY

Water quality is greatly improved by oysters filtering out suspended matter. This improves sunlight penetration to the seabed and benefits a range species including submerged aquatic vegetation.

REDUCING NITROGEN LEVELS

Estuaries tend to have very high levels of nitrates from agricultural run-off and waste water discharge leading to eutrophication. Oysters remove these excess nutrients from the water column.

HERITAGE VALUE

Native oyster fishing and cultivation have long been at the heart of coastal communities in Essex and can be traced back to Roman-times.

THE HISTORY OF OUR NATIVE OYSTER

Our native oyster has been with us for as long as we can see back in our human history.

Below is a timeline showing just how important native oysters have been to us and also some of the threats that they have faced over the years.

The 21st Century

Essex Native Oyster Restoration Initiative is formed in 2011 and in 2013 The Blackwater, Crouch, Roach and Colne Estuaries MCZ is designated for the native oyster and their associated beds.  Further protection was granted in 2018 through a Kent & Essex Native Oyster Permit Byelaw, confirming the legal protection of the fisheries management plan and Restoration Box. Physical restoration in the Restoration Box began in mid-2019.

The 20th Century

Oyster landings began to plummet in England and Wales, dropping from 26 million to 7 million over 30 years to 1948.

The catastrophic freezing weather event of 1963, the introduction of the toxin Tributyltin into waters in 1980 and the emergence of the parasite Bonamia ostreae in 1983 all led to even further declines in oyster numbers. In 1979, oystermen formed the Blackwater Oystermen’s Association to jointly manage and cultivate the several order and in 1984, acquired the controlling interest in the Tollesbury & Mersea Native Oyster Fishery Co. Ltd and began the slow process of increasing oyster stocks

The 19th Century

A boom in the demand for native oysters led to 200 million being sold annually in London alone and the industry employed 15,000 boats and 50,000 people. As shipping technology improved and demand increased across Europe, the native oyster populations suffered significantly. In 1876, The Tollesbury & Mersea Native Oyster Fishery Co. Ltd was formed to enable the local oystermen to manage the oysters in the River Blackwater.

The 17th Century

Export of oysters became vital for Colchester, with peak exports in 1682 at over 4,000 bushels shipped overseas, most likely to its dominant trading partners in the Netherlands.

From the Stone Ages to the Middle Ages

Archaeological records show that native oysters have long been an important part of our cultural heritage – the Romans particularly valued them and would sell oysters along the main Roman road to London. There are even records of valuable oyster beds in the Domesday Book in 1086.

THREATS TO OYSTERS

Threats to oysters have mainly come around as a result of human actions.

Little changes that humans have done can influence the native oyster population in a huge way.

OVER HARVESTING

700 million oysters were consumed in London alone in 1864; the harvest fell from 40 million in 1920 to 3 million in the 1960s due to overharvesting.

What's the solution? ->

Manage oyster fisheries sustainably

  • The development of a clear, mutually agreed and beneficial management plan will help to inform all stakeholders on how to ensure sustainable fishing.
  • Being mindful of the ecosystem services oysters provide when they remain in the sea.
  • We are researching the use of novel and innovative financing mechanisms to ensure successful restoration and long term, self-sustaining conservation and social impact.

HABITAT DEGRADATION

Historical unsustainable fishing practices have led to the oysters’ preferred habitat being degraded beyond use.

What's the solution? ->

Improved Protection

  • We need to improve protection of these vulnerable wild native oysters and their beds through marine protected areas as a priority for coastal habitat management.

Restoration and Recovery of the native oyster

  • Recover the spawning population so that there are more juvenile oysters in the water column.
  • Improving the seabed substrate by adding more hard shell and gravels (cultch) so these juvenile oysters can settle out and grow.

POLLUTION

Pollutants from human activity can have a drastic effect on oyster numbers, as was discovered in the late 20th century when Tributyltin (TBT), an industrial paint used to paint the underside of boats, was found to leech from boat hulls into the surrounding waters. This drastically reduced the growth and reproductive success of the native oyster.

What's the solution? ->

Addressing threats such as nutrient pollution and excessive sedimentation will help oysters recover. Understanding how substances making their way into coastal waters effect oyster growth and reproduction is important to ensuring long term improvements to water quality. As their numbers recover, water quality is greatly improved as they filter out suspended matter improving sunlight penetration to the seabed.

DISEASE

The parasitic protozoan Bonamia ostreae is known to have caused massive mortalities of the native oyster in France, the Netherlands, Spain and the UK. Bonamia rarely result in signs of infection and usually is only detected when there is increased mortality in the population.

What's the solution? ->

  • Some areas have a known presence of Bonamia ostreae, the protozoan parasite that is known to threaten native oysters.
  • We are currently researching how we can build in resistance in the oyster populations to buffer the threat of bonamia.

 

COMPETITION AND INVASIVE SPECIES

The bulk of the oysters produced in the UK are the introduced Pacific oyster Crassostrea gigas. The cultivation and spread into the wild of the Pacific oyster is a threat as there is a possibility that it may take over the niche of the native oyster and limit the opportunities for recolonization.

What's the solution? ->

Oyster grounds have been degraded in some areas by the slipper limpet Crepidula fornicata, an invasive non-native species. This species is a filter feeder creating ‘mussel mud’ which degrades the grounds and hinders recruitment to oyster beds, although the dead shells provide a surface on which the oyster spat do settle. The American oyster drill Urosalpinx cinerea is an invasive species, which preys on the native oyster.

 

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