Alexander W Shakspeare, Tom C Cameron, Michael Steinke

The Pacific oyster (Magallana (Crassostrea) gigas) was introduced to UK waters in the mid 20th century and currently accounts for over 95% of UK oyster fishery landings. Recently however, its non native origin has led policy makers to consider a limit on UK oyster aquaculture operations. M. gigas is effectively naturalised in the UK, with multiple records of populations originating from non local sources, including from outside the UK. Neighbouring countries, most notably France, treat M. gigas as a naturalised species. The naturalised status simplifies regulation and enables the fishery to provide large quantities of nutritious and sustainable food, supporting employment in coastal communities. Further to this, alongside the potential for detrimental effects this species could have on natural habitats, M. gigas presence can have substantial positive environmental impacts, for example, for improving water quality and by providing living breakwaters for contemporary coastal protection schemes. Our review suggests that efforts to reduce the spread of M. gigas in England are unlikely to have the desired long-term effect and will fundamentally fail due to introductions in Scotland and larval connectivity throughout the southern North Sea. We recommend that UK policy on M. gigas should be updated to reflect the environmental and socioeconomic benefits of Pacific oysters to the shellfish fishery and to open its utility for the provision of nature-based solutions in the adaption to the effects of sea-level rise. Additional location-specific management interventions should focus on suitable mitigation for sensitive sites or to slow spreading events on a case-by-case basis.