Storage and Detoxification of Bivalve Molluscs as a Tool in a Marketing Strategy

Abstract

This study fostered partnership between scientists, shellfish growers, water treatment engineers, economists and regulators. The objective was to optimise land-based post-harvest treatments in such a way that oyster and mussel marketing could continue during toxic blooms of Dinophysis acuminata (DSP) and Alexandrium minutum (PSP). Among the different methods capable of eliminating toxic algae, sand filters reduced microalgae by 90–99 %, depending on sand grain size used, whereas immersed membranes (0.2 μm) retained 99 % of particles. However, equipment and operating costs were higher for immersed membranes. Experiments using disrupted algal cells showed that PSP and DSP toxins remained stable and soluble for 15 days following release from the cell. The soluble fractions were practically unavailable to mussels. The storage of oysters for 35 days required a re-circulating system at 16 °C, with a continuous algal food supply (Skeletonema costatum). These culture conditions provided a good balance between algal supply and sea water turnover, allowing for the conservation of mussel body condition and water quality, with regard to dissolved forms of nitrogen. The efficiency of detoxification was correlated with the ingestion of food particles. When oxidizing agents (H₂O₂) were used, detoxification kinetics followed a different course from those observed during natural decontamination processes. From an economic point of view, analysis of the type of shellfish farm provided a way to identify farms that were likely to purchase, either safe storage or detoxification equipment. Plant size was simulated as a function of the average quantity of shellfish processed.