Scottish Shellfish Farm Production Survey 2021

Health influences on the industry

A risk based surveillance programme targeting 37 shellfish site inspections was undertaken during 2021. On these visits, facilities, stock health, bio-security measures plans, movement records and details required for authorisation were checked. Records were checked remotely for a further 15 sites. The number of site inspections was reduced in 2021 due to COVID-19 travel restrictions in Scotland.

Most of the reported mortalities during 2021 were attributed to: predation from wild ducks, starfish, crabs and oystercatchers; fouling by sea squirts; adverse weather conditions including storms and temperature extremes; damage due to grading and handling and from natural causes. It is the responsibility of shellfish farmers to inform Marine Scotland of any abnormal or unexplained shellfish mortality on their sites (see guidance on shellfish mortality in Appendix 1.

Approved zone status for bonamiasis, marteiliasis and Ostreid Herpes Virus-1 Microvariant (OsHV-1 µvar) continued to protect the health of both wild and farmed susceptible shellfish stocks in Scotland's waters (Fish Health Inspectorate).

The whole coastline of Great Britain is recognised as free from infection with Marteilia refringens although there are movement restrictions in place on the River Tamar in Cornwall and Devon.

Also the whole coastline of Great Britain is recognised as being free from infection with Bonamia ostreae except the following areas which are covered by movement restrictions:

• Loch Sunart in Highland region;
• Dornoch Firth in Highland region;
• West Loch Tarbert in Strathclyde region;
• Lynn of Lorne, Loch Creran and Loch Etive in Strathclyde region;
• the south coast of Cornwall from Lizard to Start Point;
• the coast of Dorset, Hampshire and Sussex from Portland Bill to Selsey Bill;
• the area along the coast of North Kent and Essex from North Foreland to Felixstowe;
• the area along the coast in south-west Wales from Wooltack Point to St Govan's Head, including Milford Haven and the tidal waters of the East and West Cleddau river;
• Menai Strait.

(see Appendix 3, for maps of areas under movement restrictions for Bonamia ostreae in Scotland)

The whole coastline of Great Britain is recognised as free from OsHV-1 μvar except for the following areas:

• Essex, Kent and Suffolk (Felixstowe to Ramsgate)
• Butley Creek, Suffolk;
• Poole Harbour in Dorset;
• the River Teign in Devon.

Movements and imports of shellfish species susceptible to infection by Marteilia refringens, Bonamia ostreae and OsHV-1 μvar, into the Great Britain health zone, must originate from another zone or country recognised as free of that disease and are required to be accompanied by a health certificate. Movements are allowed from disease free areas to non-approved areas, as well as those for direct human consumption without re-immersion in any other sea water areas.

In 2021, there was a continued demand for imported mussel and Pacific oyster spat in Scotland. The industry should be aware of the increased disease risk with the introduction, movement and deposit of stock on site and the importance of ensuring good bio-security practices when sourcing shellfish from other areas