Eutrophication is a major problem in most coastal waters in the Baltic Sea. Mussel farming can be an appropriate measure to remove nutrients, increase water transparency and to improve water quality. However, today mussel farming does not exist on a commercial basis in the southern Baltic Sea. The main obstacles are a lack of tradition, missing profitability and, cold winters. Ice sheets and drift ice are a threat for mussel farms and make investments risky. Data of the last 80 years show a clear reduction in the number of ice days. Climate change model projections indicate that this trend will speed up. In particular, winters shall become much warmer during this century. Already today, drift ice at the southern Baltic Sea is limited to a few years within a decade. In the future, winters with lasting ice cover will be the exception. Further, mussels benefit from increasing temperatures and farming will become more profitable. Against this background mussel farming becomes a realistic option and a potential new business in our coastal waters.
This chapter explores several aspects of mussel farming and establishes a first basis for a practical implementation. Two native mussel species are suitable for farming in the Baltic: The Blue mussel (Mytilus edulis), which is cultivated in many marine waters worldwide, and the Zebra mussel (Dreissena polymorpha). The Zebra mussel prefers low salinities (< 5 PSU) and is not used for farming, yet. As long as critical mussel densities are not exceeded, mussel farming is an environmental friendly and sustainable way to produce high quality food. For farming in the shallow coastal waters of the German Baltic coast, a long-line system with looped growing lines is suggested. Zebra mussels are considered to be too small for human consumption. Mussel meal, as a substitute for fishmeal, is the most promising product. The ongoing increase in fishmeal demand and prices might make the complex and costly processing more profitable. However, mussel farms in the southern Baltic will require additional funding for their ecosystem services to become economically viable. The EU-Water Framework Directive might offer opportunities.