Exploring strategies for improving productivity of on-bottom mussel cultivation: A Danish perspective

Mussels have been identified as a promising future food due to their potential contribution to sustainable food source for the future and healthy diets. However, wild populations and blue mussel production in the European Union have declined over the past decades. Traditional mussel bottom culture in Europe involves relaying seed from wild or aquaculture sources to licensed seabed plots, requiring relatively low investment. Nonetheless, in recent decades, stricter environmental regulations have reduced access to wild seed, increasing dependence on suspended seed and raising production costs related to seed sourcing. This study investigates the cultural practices that affect the productivity of subtidal on-bottom mussel cultivation in Denmark (Limfjorden) and compares seed sources: the traditional wild and emerging suspended seeds. Here we calculated for the first time that, on average, the Relative Biomass Production (RBP) is 0.43 for on-bottom relay plots of fished seed and 0.59 for culture plots of suspended seed, indicating that most beds yield approximately half of the relayed biomass. The RBP in Limfjorden is lower than in other European regions. On-bottom mussel cultivation in the Limfjorden has significant potential and can contribute to future food security. However, for this potential to be realised, access to grow-out sites and seed sources must be secured.