| Summary: | Crassostrea gigas is native to South East Asia and Japan. Due to the species hardiness and fast growth, the spat has been commercially exported to aquaculture industries worldwide. The first introduction of C. gigas into the UK for commercial cultivation is thought to have been in 1926. The harvesting of bivalve molluscs for human consumption is a traditional activity within the Fowey Estuary, Cornwall, UK (a recently designated Marine Conservation Zone). Anecdotal evidence suggested wild settlement of C. gigas throughout the estuary. Current abundance and distribution of wild populations was determined by timed shore searches where both ‘young’ (≤ 6cm in length) and ‘mature’ (> 6cm) C. gigas individuals were recorded. A SACFOR scale was used to determine categories of abundance found at each site with presence. The length of random individuals within each site was also recorded along with other factors such as substrate type. Surveys of Fowey Estuary stakeholder groups were used to produce a thematic cost-benefit analysis of the ecological and socio-economic impacts of the aquaculture industry and wild settlement within the estuary. Pont Pill is an area where the aquaculture of C. gigas was first established and showed the highest densities of individuals. Few ‘young’ individuals were recorded throughout, suggesting little recent settlement. Areas within the MCZ boundary surveyed showed a lack of presence, likely due to unsuitable substrate. The Bonferroni correction inferred that both site 12 and 5, in close proximity to the aquaculture activity, had the smallest median lengths suggesting most recent settlement. Sites south of Pont Pill showed potential for future settlement. The aquaculture industry is important to a number of stakeholders within the Fowey, as is the visual landscape aesthetics and recreational use of the shores. Future monitoring would be needed to determine whether the populations are self-sustaining and in turn to decide whether management measures are required here.
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