The economic impacts induced by the harmful effects of pollution or negative natural events are heterogeneous and depend on the event type and intensity, as well as the characteristic make-up of agents affected. This vulnerability analysis evaluates how each agent (or group of agents) is potentially affected by an external stress or event with respect to risk of exposure, sensitivity or intensity of subjection, and coping capacity of these agents in order to avoid or reduce its effects. Using a comparative formulation model, the aim of this paper is to quantifiably assess the vulnerability of shellfish farming linked to bacteriologic pollution. An analysis of the vulnerability concept and the construction of pertinent indicators are presented. The analysis is then applied to the Thau Lagoon, a shellfish farming production area of the French Mediterranean; this industry is threatened by different ecosystem disturbances including the increase of microbiologic contaminations of the lagoon׳s catchment which often results in commercial bans. The commercial bans associated to micro-bacteriologic pollution have a varied effect on shellfish farming companies. A field survey was used to gather information about the sector and the companies themselves. This paper shows that the strongest companies (minimally affected by commercial bans compared to other companies in the sample) invest in storage technology and product diversification, which mitigates negative impacts from commercial bans. Companies that have large capital are no less impacted than those without much capital. Potential policy and community structured assistance can support the shellfish industry using this type of quantitative vulnerability formulation.