Harmful and toxic algal blooms (HABs) are an increasing concern for marine social-ecological systems. These unpredictable events threaten human health and may affect the viability of economic activities such as shellfish fisheries due to harvesting bans. Monitoring and early warning systems are developed to support management decisions to mitigate and reduce impacts. Nevertheless, HAB alert systems currently only focus on the environmental dimensions to identify the risk of bloom occurrences. Other socioeconomic dimensions associated with HABs are generally not taken into account to support decision making. Integrating information on the economic risk of HABs and on adaptive strategies of impacted communities would provide essential insights for decision makers. This study presents an analysis of how the potential impacts of HAB-related restrictions on economic activities can be effectively assessed to support decision making. A vulnerability-based approach is developed and applied to the case study of the French scallop fishery in the eastern English Channel. The results showed clear differences in vulnerability patterns between the studied fishing fleets despite their similar exposure. This is associated with the heterogeneity in individual characteristics in terms of sensitivity level and adaptive strategies. This research highlights the important effect of social factors such as adaptation in the magnitude of HAB impacts and supports the relevance of the vulnerability approach in the assessment of socioeconomic impacts of such events. Combining environmental and socioeconomic factors through a composite index can bridge the existing gaps in addressing and mitigating HAB impacts.