Review of toxic episodes and management strategies in the Danish mussel production

Denmark has in many years been one of the world’s main producers of blue mussels caught from natural banks. The Danish mussel aquaculture sector is now growing. The Danish production areas have been regarded as “low risk” areas with respect to toxic algae and occurrence of marine biotoxins. The change to more production of cultured mussel results in higher risk for occurrence of marine biotoxins because of the closer interaction between toxic algae and mussels. Results showing the difference between content of marine biotoxins in bottom mussel and cultured mussel from the same production areas will be presented. The presentation will be based on results from toxic episodes in recent years and will cover different aspects and changes made in the Danish mussel monitoring system in the last years to improve both the food safety and the commercial conditions for the mussel producers. This includes use of heat treated mussels as matrix for marine biotoxin testing and consequently a reduction of the maximum limit for lipophilic toxins by a factor of approximately two, use of chemical methods for verification and extra precaution measurements during risk periods, and use of measurement of actual algae cell toxicity of potential toxic algae in combination with algae cell number and mussel toxicity for opening or closing of production areas.