Evaluation of a floating upwelling system for nursery culture of the Greenshell ™ mussel (Perna canaliculus)

Major losses of early juvenile seed mussels or spat are a typical feature of the aquaculture production cycle for many mussel species. These losses are caused by a variety of factors including predation, mortality, and the innate migratory behaviour of spat. In this study, we examined the potential to reduce spat losses by using a floating upwelling system (FLUPSY) for raising the spat of New Zealand's Greenshell™ mussel (Perna canaliculus) to a larger size before transfer to a coastal mussel farm. The losses of spat experimentally cultured within a FLUPSY over 85 days were much lower compared to spat that were seeded directly into coastal waters (78% vs. 99.8%). At the end of the 85-day nursery culture period, spat in the FLUPSY were 7% larger despite being cultured at higher densities. The losses for two size classes of spat that were raised in the FLUPSY remained relatively high (83% and 95% for spat seeded out at 6.6- and 15.5-mm shell length (SL) respectively) after two months of being experimentally seeded onto a coastal mussel farm. However, these losses are lower than have been reported previously for this species during this stage of production. The results from this study suggest that the addition of a FLUPSY nursery stage to the Greenshell™ mussel production could greatly reduce spat losses and improve production efficiency.