Emersion survival manipulation in Greenshell™ mussels (Perna canaliculus): Implications for the extension of live mussels' shelf-life

Farmed adult Greenshell™ mussels were exposed to a range of conditions immediately after harvest to evaluate the effects on emersion survival and the implications for live transport. Two experiments were performed, coinciding with the mussel harvest season during summer and winter 2017. In the summer experiment, a wide range of conditions were tested to identify alternatives to be evaluated in more detail during the winter experiment. The postharvest experimental conditions selected included transient re-immersion at different temperatures, cold and heat-shock, tidal simulation, and packing with ice. These treatments aimed to either reduce postharvest stress and/or give the mussels a potentially beneficial physiological and behavioural advantage to help them cope with emersion. The mussels' responses in terms of gaping and survival differed between summer and winter, and among and within treatments. Sub-ambient temperature seawater exposure after harvest tended to improve the survival time of the mussels in both seasons, the effect being dependent on both temperature and duration of the exposure. Some of the differences observed could be explained by the conditions (in the wild and in the laboratory) to which the mussels were exposed before emersion and the different capability that each mussel has to cope with stress. However, the exact mechanisms driving these changes are not fully understood and require further investigation. This study, nevertheless, indicates that emersion survival (i.e. live mussel shelf-life) could be extended by re-immersion after harvest combined with a sub-lethal cold-shock followed by immersed recovery before transportation. If the commercial shelf-life of live product can be significantly extended, the implications for food quality and safety will also need to be evaluated. A similar approach could be applied in other shellfish such as other species of mussels as well as oysters or clams to improve shelf-life, considering their physiological capabilities and behaviour and how those are affected by environmental conditions in different seasons or regions.