Research

Modelling mussel larval distribution for optimal site selections of mussel farming

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Abstract

Eutrophication is one of the largest threats to the Baltic Sea manifested by algal blooms, turbid waters, loss of submerged vegetation and hypoxic and anoxic conditions at the sea bottom in large areas. It is well known that marine suspension-feeders possess a significant capacity for clearing the water column of particles. The potential of using bivalves such as blue mussels to mitigate effects of eutrophication in the coastal zone has been proved to be cost-effective in Danish waters. However, it is still a challenge to optimize mussel farms and mussel production and thereby further reduce costs in order to compete with other mitigation measures. The farm design and locations need to be adapted to different environmental conditions in order to handle e.g. high predation pressure, low salinity, exposure to high wind, waves or ice coverage, but also in terms of efficient mussel larvae settling on the long-lines. Spawning takes place in the natural mussel beds in May-June and the resultant larvae are spread by the water currents to other areas before settling on the bottom or on the long-lines in the mussel farms. In the following study, we used 3D ecosystem modelling to estimate the mussel larval distribution on fine spatial and temporal scales in a local set-up of the Limfjorden. We coupled a 3D physical Limfjord model with an agent based model (ABM) using the Flexsem system, where mussel larvae were defined by several biological parameters. The model provided maps of mussel larvae distribution and will be used for site-selection processes of mussel farming in the Limfjorden. These results are of fundamental importance for the development of mussel farming as a measure to mitigate eutrophication.