Stability of subtidal blue mussel beds in eutrophic coastal areas

Mussel populations (Mytilus edulis) around the coasts of Europe and the North Atlantic are often ephemeral and have notably experienced a large decline in abundance. Since 1993, annual blue mussel stock surveys have been carried out in the Limfjorden, Denmark. We used the stock survey data combined with electronic monitoring fishing data and a Mechanistic Model for Limfjorden, providing environmental data to investigate the impact of various stressors of blue mussel beds. Multiple factors were found to affect the longevity of subtidal mussel beds in Limfjorden. Predation by starfish, fishing activities, shell length of the mussels, amplitude in summer temperature, consecutive days of oxygen depletion and stratification had a negative impact on the bed longevity. Conversely, increased biomass and the presence of multiple cohorts demonstrate stabilizing effects on mussel beds. These analyses can help inform environmental, conservation, and fisheries managers on the long-term trends of population dynamics and gain a deeper understanding of what factors can affect mussel bed longevity in the context of declining stocks.