Scottish Shellfish Farm Production Survey 2011

Scottish Shellfish Farm Production Survey 2011 produced by Marine Scotland Science

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In accordance with Council Directive 2006/88/EC, a risk based surveillance programme targeting 139 shellfish site inspections was undertaken during 2011. On these visits, facilities, stock health, bio-security measures plans, movement records and registration details were checked. In addition, native oysters were sampled from nine sites, including four 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 2011. 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, oyster catchers and fouling by a polychaete worm. Reports of high, unexplained shellfish mortalities generated six shellfish diagnosis cases during 2011, at sites holding mussels, native and Pacific oysters. In addition, investigations were undertaken following reports of poor mussel spat settlement during 2010. Results of diagnostic investigations suggested environmental influences, but 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).

The results of poor mussel spat settlement investigations, 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 ( Crassostrea gigas), in connection with the detection of Ostreid Herpes Virus OsHV-1 µvar.

Targeted surveillance continued in 2011 on thirteen sites holding the susceptible Crassostrea gigas, no evidence of the presence of Oyster Herpes Virus was found in Scottish waters; surveillance is to continue in 2012 under article 43 of Directive 2006/88, testing production areas with the aim of preventing imports from infected areas into Scottish waters.


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