There is an international pressure to increase the worldwide expanse of marine mussel farms. However, the mussel farms are challenged with environmental problems such as mucilage aggregate events. Thus, it is essential to assess the effects of mucilage on the mussel aquaculture and to eradicate the harm and socioeconomic effects they confer on society. Our study addressed this issue by establishing a demographic baseline for commercially important mussel species prior to the proposed aquaculture in the area. This baseline was established at a recently set up commercial mussel farm located approximately 4km north of Erdek port and around 2km from Ocaklar port in the Marmara Sea region of Türkiye. Monthly samples of spats attached to the collectors and mussel meat yields were addressed, and seawater temperature and chlorophyll a contents were measured throughout this study (36 months) conducted at a commercial mussel farm. Year-round biological data from 2019 to 2022 were recorded before, during, and after the mucilage event on the Mediterranean mussel, Mytilus galloprovincialis. Moreover, samples were taken from an area inside the mussel aquafarm. As a result of this study, differences before, during, and after the mucilage aggregate event were detected in the number of the Mediterranean mussel spat attached to the collectors and the meat yields of the farmed mussels. This demographic baseline is the only data available, at a sufficient spatial and temporal resolution, for evaluating the effects of a mucilage aggregate event in the mussel aquafarm, and it fills an important data gap for risk assessment.