Commercial bans due to harmful algal blooms (HABs), which are natural events, question the sustainability of human activities in marine and coastal areas. A risk assessment of these bans is important to support decision-making to better manage and mitigate their impacts. However, data are sparse and difficult to collect. The dataset presented in this paper includes “estimated closures of scallop fishing areas” due to HAB toxicity along the French coasts of the English Channel. The closure data were simulated for each scallop (Pecten maximus) fishing area through an algorithm applied to the in situ dataset from the French monitoring network REPHYTOX. The methodology of the production of closure data consists of comparing phycotoxin concentration in scallop to regulatory thresholds of phycotoxins, and then, simulating the number and duration of closures based on the monitoring strategies and closure mechanisms as defined in the regulations. These data only cover closures related to regulatory threshold exceedances of phycotoxins in shellfish. Closures induced by the lack of sampling or other reasons (e.g., failures in toxin analysis) are not included in the dataset because of the lack of information. Data are produced during the scallop fishing season. Facing the non-existence of such a closure database due to the lack of centralized management of local closure decrees, this dataset can be used to analyse the management strategies to deal with HABs and to highlight the governance challenges related to these strategies. It is also useful to study the link between the ecological and the socioeconomic dimensions of HABs, and to describe how toxin concentrations in shellfish translate into socioeconomic impacts and management challenges. This methodology can be applied to other species, other areas and other economic activities.