The endangered European native oyster Ostrea edulis (L) and creation of Marine Conservation Zones: a win – win scenario for fisheries and conservation?

The abundance and distribution of Ostrea edulis and O. edulis beds have been contracting for many hundreds of years as a result of anthropogenic factors, leaving behind the legacy we observe today of a fragmented and severely impacted habitat. In 1995, O. edulis (and their associated beds) was designated a Biodiversity Action Plan Species and Habitat, and in 2009, as a Feature of Conservation Importance (FOCI) within the UK Marine & Coastal Access Act 2009. To protect the species, a greater understanding of its abundance and distribution and age structure was needed to ensure designation of Marine Conservation Zones (MCZ). Between 2012 – 2015, Essex Wildlife Trust, Blackwater Oystermans Association and the University of Essex undertook a study of density and distribution of O. edulis across the 282 km2 area known as the Blackwater, Colne, Crouch & Roach recommended MCZ (BCCR). This showed that population aggregations were restricted to four main areas. Size structure within two of these four areas showed a significant lack of <40 mm (shell length) individuals. The highest densities and most even size structure for O. edulis populations were all located within actively managed harvesting areas. The study also found low concentrations of larvae in the water column during the breeding season (May – October) suggesting that veliger production is limited which may prevent recovery of populations. In 2013, the BCCR was designated as an MCZ, as a result of the study the recommendation was made to set the conservation objectives from ‘maintain’ to ‘recover’. Subsequently, fisheries restrictions have been implemented to retain breeding stock and a management plan of active restoration implemented. The results emphasise the importance of working in partnership with the fishing industry, statutory nature conservation organisations and NGO’s to recognise traditional aquaculture practices as a conservation tool for the restoration of a MCZ protected feature.