The method here was to study 6 different sites in the Baltic Sea with project farms: The Musholm farm in the Great Belt (Musholm), Kieler Meersfarm in the Kiel bay (Kiel), a pilot farm belonging to Latvian institute of Aquatic Ecology outside Pavilosta coast (Pavilosta), a farm rent by Kalmar municipality in the Kalmar Sound (Byxelkrok), the East Sweden Aquaculture centre farm in St. Anna archipelago (St. Anna) and an associated farm established by Vormsi Agar OÜ outside Vormsi island (Vormsi). This report describes the activities and observations documented by our farm managers in the so-called “Mussel farmers Log” during a 2.5-year period. Farming and harvest techniques and results, no. of work hours and boat hours, technical problems, impact of ice and other site-specific conditions, conflicts with neighbors, fate of the mussels, predators and other observations are reported. We also describe the different technical setups of the farms, and impact of the environmental conditions that characterize each of our chosen mussel farm sites. We have analyzed the results in terms of harvest outcomes, differences in work effort spent on similar operations, investment costs and operational costs. Based on the limited number of farms we cannot conclude if one farm system is more efficient than the other, but it seems that anchoring, flexibility of the materials, buoys and logistics is very important, while specific substrates and mesh sizes are not key factors in the production of small mussels. At exposed sites, stronger (and thus more expensive) farm constructions and work-vessels were needed. Too strong current and wave-impact, as well as predators, had very negative effects on the production costs. The most successful sites for mussel farming in this project were found in the fjords in western Baltic and in archipelagos of the Baltic proper.