Feld L, Larsen MM, Jakobsen HH, Göke C, Hendriksen NB, Rømer JK, Mohn C & Jensen AN. 2021. Sanitary survey rapport 14. Flensborg Fjord. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 94 s. - Teknisk rapport nr. 206. http://dce2.au.dk/pub/TR206.pdf
Regulation (EC) No 854/2004 of the European Parliament and the Council of 29 April 2004 lays down specific rules for the organisation of official controls on products of animal origin intended for human consumption. Classification of production areas for live bivalve molluscs etc.[1] and the associated sampling plan are required to be based on so-called ”sanitary surveys”. A sanitary survey is an assessment of the interactions between potential sources of microbial pollution, climate conditions and oceanography in the area. The EU Commission guidance for making a sanitary survey has formed the basis for this report. However, in certain cases, the Danish practice for microbiological sampling frequency and the previous classification on the basis of this is used. The Danish practice is described in ”muslingebekendtgørelsen”, which is summarised in Appendix 11.
The report covers the Danish area in the northern part of Flensborg Fjord, which spans from the inner part of the fjord by Flensborg city to the west and includes the broader area in Sønderborg Bay and the narrow Hørup Hav and is flanked to the east by the eastern end of Kegnæs. The area covers three production areas P81-P83. In Flensborg fjord, no permissions for mussels farming are registered and commercial fishing for mussels was only registered in P83. Within the latest 10-year period (2010-2019), catches of mussels were recorded in the period 2015-2019, while no catches were recorded prior to this. Only catches of blue mussels (Mytilus edulis) have been registered and with annual amounts of 60-662 tonnes per year.
The report is supported by publicly available data from the monitoring of microbiological contamination in the area in Flensborg Fjord where the concentrations of E. coli and Salmonella are determined in samples of mussels etc. taken at different sampling points within each production area. The report points to the most precautionary fixed sampling points for future monitoring. For the use of this report, data and information have been collected through web pages from, for instance, municipalities and Statistics Denmark (Danmarks Statistik). Since these web pages are not continuously updated, it cannot be guaranteed that the accessed data will be persistently available.
From the Danish mussel surveillance, a limited set of historical data is available of E. coli in mussels etc. collected from Flensborg Fjord. During the last 10 years (2010-2019), a total of 62 samples have been analysed for E. coli from the whole area. Out of these, 61 samples were from P83, while only one sample was from P81. The remaining production area (P82) was not represented in the sampling data. From the two active production areas, five samples have additionally been analysed for Salmonella during the 10-year period, with four samples from P83 and one sample from P81. All samples for Salmonella were negative. Since there were no active commercial production facilities within Flensborg Fjord, all samples were collected from the bottom and all samples represented blue mussels.
The overall data from the area Flensborg Fjord revealed a good microbiological hygiene in the investigated samples with all of the 62 samples at low levels ≤ 230 MPN E. coli/100 g, and out of these, 18 samples (45%) were below the limit of detection with < 18 MPN E. coli/ 100 g. No samples were positive for Salmonella.
In summary, the sanitary survey of Flensborg Fjord identified a good micro-biological hygiene with low levels or no microbial contamination in the production area P83. However, only a limited set of microbiological data exists for P81, and no data is available for P82. Consequently, the data was insufficient for classification of these two areas. The limited data material prevents a statistical assessment of pollution from E. coli within the production areas, years or seasons and a comprehensive assessment of the hygiene status within the production areas was not possible. This implies that the impact of potential sources of pollution on the production areas could not be satisfactorily evaluated.
Based on an assessment of sources and transport routes for microbiological contamination (sanitary survey) verified as far as possible against historical microbiological data from Flensborg Fjord, a microbiological monitoring programme is recommended for each of the production areas P81-P83. In each of the recommended monitoring programmes, proposals for a sampling location, classification status (preliminary or permanent) and a sampling plan are outlined.
Based on the results from the sanitary survey of the production areas, supported by the historical data sets on the number, frequency and E. coli concentration , it was assessed that only the individual production area P83 was considered suitable for permanent classification with a future sampling frequency of at least eight samples per year over a three-year period. Assignment of a permanent classification was not possible for the two other production areas, P81 and P82, due to lack of sampling in the past year (2019) and/or insufficient numbers of analysed samples (less than 24) within the past three years. If unclassified areas are to be upgraded to permanent classification, the EU guideline requires that the collected data should include at least 12 samples for the latest six months or data from 24 samples over the last three years.
The report is divided into main chapters that provide a summary of identified microbiological contaminants. Appendices 2-8 serve as starting point of the main chapters. Appendix 9 is a detailed review of all historical microbiological data from mussel monitoring consisting of the fishery’s own-check and the Danish Veterinary and Food Administration’s[2] verification projects of the industry’s microbial monitoring. It was decided that a so-called ”shoreline survey” is unnecessary because all possible sources of sanitary contamination are described in the sewage plans for the cities in the area, the beach water quality monitoring and in the analyses of the Ministry of Environment and Food under the auspices of the Water Framework Directive.
