Using the new SEICAT methodology to study the socio-economic impacts of the American blue crab Callinectes sapidus from Marchica lagoon, Morocco

The majority of alien species are known to have socio-economic effects by impacting various components of human well-being (security, material and non-material assets, health, social, spiritual and cultural relations, freedom of choice and action). The evaluation of the impact of invasive species is one of the critical stages in setting priorities for policy and management actions, requiring assessment systems that allow comparison of impacts on different taxa, ecosystems and socio-economic contexts. Socio-Economic Impact Classification of Alien Taxa (SEICAT) is the methodology that can facilitate these comparisons. The essential feature of this approach is that it uses changes in people's activities as a common measure to assess impacts on well-being. Impacts are assigned to one of five levels, from Minimal concern to Massive, according to semiquantitative scenarios that describe the severity of the impacts. The taxa are then ranked according to the highest level of deleterious impact that they have been recorded to cause on any constituent of human wellbeing. To demonstrate the usefulness of the system, we have classified the impacts of the American blue crab (Callinectes sapidus) in the Marchica lagoon, Morocco. These have shown a variety of impacts on human wellbeing, scoring the "Minor Impacts". The classification provides a consistent procedure for translating the wide range of measures and types of impacts by ranking the levels of socio-economic impact, allocating based on the best available evidence of proven deleterious effects, and being applicable to all taxa and a range of spatial scales. Surveys specifically tailored to capture the distinction between socioeconomic impact classes would strengthen our confidence in evaluations and to could better inform priority setting and decisionmaking.