Scottish Shellfish Farm Production Survey: 2012 Report

Health influences on the industry

In accordance with Council Directive 2006/88/ EC, a risk based surveillance programme targeting 118 shellfish site inspections was undertaken during 2012. On these visits, facilities, stock health, bio-security measures plans, movement records and details required for authorisation were checked. In addition, native oysters were sampled from six sites, including two wild beds, for the notifiable diseases bonamiasis (causative agent, protozoan parasite Bonamia ostreae) and marteiliasis (causative agent, protozoan parasite Marteilia refringens). Results were negative. Native oyster is a species known to be susceptible to these shellfish diseases. Movement restrictions placed due to confirmation of the presence of Bonamia ostrea, remained in place in Loch Sunart and in West Loch Tarbet during 2012. Movement restrictions in place covering both sea lochs prevent the relaying of native oyster from them (see Appendix 2 for maps of areas under movement restrictions). Approved Zone status continued to protect the health of both wild and farmed native oyster stocks for the remainder of Scotland's waters.

Mortalities were attributed to predation by eider ducks, crabs, starfish or oyster catchers, fouling by a polychaete worm and extreme weather conditions. Reports of high, unexplained shellfish mortalities generated nine shellfish diagnosis cases during 2012, at sites holding mussels and Pacific oysters. Results of diagnostic investigations showed no association with notifiable diseases. It is the responsibility of farmers to inform Marine Scotland of any abnormal or unexplained shellfish mortality on their sites (see guidance on shellfish mortality in Appendix 1).

2012 saw a considerable increase in the importation of mussel seed, for on-growing, into Scotland to supplement the vagaries in natural settlement. The industry should be aware of the increased disease risk with the introduction of pests and pathogens, and the importance of ensuring good bio-security practices when sourcing shellfish from other areas.

The results of poor mussel spat settlement investigations in 2011, including a questionnaire to industry, indicated that poor spat settlement and mortality was not widespread in Scottish waters, although a major impact on certain individual producers. The causes are associated with environmental variables, guiding industry to consider focussed spat fall monitoring to help predict spat settlement in time and space. Communication among industry, MS policy and scientists is to continue to determine the need and focus for possible research and development.

In March 2010 Commission Regulation No. 175/2010 was introduced to implement Council Directive 2006/88/ EC as regards measures to control increased mortality in Pacific oysters, in connection with the detection of Ostreid Herpes Virus OsHV-1 µvar.

Targeted surveillance continued in 2012 on 13 sites holding susceptible Pacific oysters, no evidence of the presence of Oyster Herpes Virus has been found in Scottish waters to date. Active surveillance is to continue in 2013 under article 43 of Directive 2006/88/ EC. A submission (Declaration from the United Kingdom for disease-free status for Ostreid herpes virus (OsHV-1 µVar) under Article 43 of Council Directive 2006/88/ EC) has been made following the third complete year of surveillance for the UK. http://www.scotland.gov.uk/Topics/marine/science/Research/aquaculture/diseases/notifiableDisease/oshvdec