Harmful Algal Blooms (HAB) events may have serious economic consequences for shellfish farmers. When toxic algae blooms threaten human health, public authorities may decide to shut down the farming business for a while, i.e. ranging from a few days to several weeks or months, according to the severity of risks. The impact of closures being temporally and spatially distributed, shellfish farmers can avoid the risky zones or develop adaptive strategies to mitigate the economic consequences and therefore reduce significantly their business sensitivity to HABs. A sequential approach by optimal matching analysis is applied to an original data set of shellfish area closure decrees between April 2004 and December 2018 in Southern Brittany and Pays de la Loire (France) to build a typology of 79 aquaculture zones affected by various HAB and microbiological hazards (ASP, DSP, Norovirus, E. Coli, oil spills). The hypothesis is that the degree of exposure to the HAB hazard assessed by zonal closures may not be correlated to the level of sensitivity revealed by the economic results of the shellfish farming industry which can develop avoidance strategies.

有害的藻华（HAB）事件可能会对贝类养殖者造成严重的经济后果。当有毒藻类的繁殖威胁人类健康时，根据风险的严重程度，公共当局可能会决定关闭农业业务一段时间，即从几天到几周或几个月不等。封锁的影响在时间和空间上是分散的，贝类养殖者可以避开危险区域或制定适应性战略以减轻经济后果，从而大大降低其对HAB的商业敏感性。诺如病毒，大肠杆菌，漏油）。假设是，通过区域封闭评估的暴露于HAB危害的程度可能与贝类养殖业的经济结果所揭示的敏感度水平无关，贝类养殖业可以制定避免策略。