SARF064: Mytilus trossulus: Managing impact on sustainable mussel production in Scotland

Start Date: 04/01/2010
End Date: 30/6/2011
Main Contractor(s): Marine Scotland Science
Other Sponsor(s):  


Limiting the potential impact of M.trossulus at the national Scale.

 Preparation of a Code of Good Practice – Months 5 - 12

1.1     Consult with the ASSG to determine the perceived scale and severity of the problem.            Month 5

1.2     Explore possible availability of statutory powers to control or manage movements of mussels. Month 5

1.3     Review status of Mytilus trossulus in Scotland (indigenous/introduced, invasive/non-invasive)

          and the implications and opportunities presented under relevant UK and EU legislation.  This

          will include  identification of any financial assistance opportunities that might support a

          M. trossulus control programme.                                                                                                  Month 5

1.4     Undertake literature review for Codes of Practice applicable in aquaculture contexts.                Month 7

1.5     Review applicability of ICES Code on Introductions and Transfers.                                                Month 6

1.6     Develop framework for voluntary Code in consultation with ASSG.                                             Month 8

1.7     Incorporate such restrictions on movements as may be acceptable to shellfish growers, possibly

          incorporating an area-based management system.                                                                     Month 8

1.8     Explore feasibility of species identification prior to movement using modern molecular biological

          methods (RT-PCR).                                                                                                                      Month 8

1.9     Draft Code of Practice.                                                                                                                 Month 10

1.10   Consult with industry and other stakeholders and prepare a final draft.                                      Month 11

1.11   Develop publicity materials (leaflets etc) in collaboration with ASSG.                                         Month 12

2) Limiting the impact/eradicating M.trossulus at the regional scale. – Months 1 - 6

2.1      Establish the relative sizes of reservoirs (farmed and wild) of Mytilus trossulus in Loch Etive study area.                                                                                                                                         Month 1

2.2      Report on the impact of removal of abandoned mussel farms within Loch Etive.                       Month 3 

2.3      Employ an epidemiological approach to assessing feasibility of options for reduction of the proportio of Mytilus trossulus including consideration of reseeding from local settlement or using seed   transferred from elsewhere.                                                                          Month 4

2.4      Undertake an economic analysis of the preferred options to include exploration of possible

           financial assistance to assist industry-driven control strategies                                                Month 5

2.5      Prepare report.                                                                                                                            Month 6


Mussel production is an important growth sector within Scottish aquaculture and significant contributor to the economy, with production having increased from just 262 tonnes in 1986 to 5,869 tonnes in 2008. The Industry was estimated to be worth up to £6million in 2008 at first sale to the Scottish economy. Mussel production in Scotland was, until recently, considered to be based exclusively on the blue mussel M. edulis, the endemic species. Recent research initiated in response to concerns from the industry has, however, identified the presence of an additional species, M.trossulus, in Scotland. Identified in significant numbers within Loch Etive, the presence of this species, which is characterised by poor meat yields and thin shells, has resulted in production losses which threaten the viability of the industry in this historically important growing area.  In addition to the negative impact experienced within Loch Etive, the detection of this species in other areas of Scotland by Marine Scotland scientists raises the issue of a potential wider impact of M.trossulus at the national scale.  Managing the impact of M.trossulus at both the regional and national scale is of fundamental importance to ensuring the long term sustainability of mussel production in Scotland.

Recent work conducted by Marine Scotland scientists working in partnership with the industry has identified the following key findings which are of significance to the potential control of M.trossulus in Scotland:

The origin of M.trossulus in Scotland remains unclear, but it may represent a relict population which has established and  flourished in the specific environment provided by aquaculture.

Regardless of origin, M.trossulus appears restricted to specific protected biological niches such as those found in farms, with no significant wild reservoir of M.trossulus having been identified.

M.trossulus is restricted in its geographic distribution within the range of the Scottish industry.

M.trossulus and M.edulis do not appear to have sufficiently distinct life history traits (eg different spawning times) that would allow management through preferential settlement of the desired species.

The significant body of scientific information regarding the distribution of M.trossulus in Scotland, now provides the opportunity to develop a science-based approach to the control of this problem. Current knowledge summarised above suggests that impact of M.trossulus within Scotland might be limited through reducing its presence and spread throughout the industry. In response to a specific SARF call and favourable evaluation of an outline concept note, this proposal seeks to evaluate viable methods for limiting/eradicating the presence of M.trossulus presence within the Scottish industry. Such an approach will require the continued close cooperation and support of the Scottish industry and will be reliant on development of strategies at both the regional and national scales. This will include evaluation of the potential to greatly reduce/eradicate the presence of M.trossulus from key local problem areas in addition to identifying mechanisms to prevent dissemination of the species within the wider industry. Both primary aims will be supported by translation of current knowledge into a code of good practice that will form the basis of an industry-lead control policy. Recommendations and practical solutions will be developed, implemented and communicated through optimal use of the combined experience of the Shellfish industry and Marine Scotland Science.