Analyse économique du contrôle d'une invasion biologique. Modélisation théorique et application à la pêcherie de coquille Saint-Jacques de la baie de Saint-Brieuc envahie par la crépidule

摘要

Biological invasions are nowadays an important challenge to biodiversity and human welfare. Managing biological invasions, which encompasses both prevention and control, is a public good and, as such, falls within the scope of cost-benefit analysis. The thesis deals with the control of an invasive species void of market value, and acting as a space competitor for a native valuable harvested species. Its first part is dedicated to a theoretical bioeconomic model describing the interacting dynamics of the two species and accounting for the undesirable consequences native stock harvesters behaviour have on the spread of invasion. In the model, control variables are the levels of harvesting effort of each species, and the target-function maximises the resource rent provided by harvesting the native stock, minus the cost of harvesting the invasive species. Static equilibrium analysis of the model provides a clear-cut alternative between asymptotic quasi-eradication of the invasive species and complete laisser-faire. Dynamic optimisation of the model displays the existence of a time-path leading to an optimal steady-state equilibrium where the native species is sustainable harvested and the invasive species is kept under control, provided units costs of native species harvesting and invaded areas cleaning, natural and anthropogenic invasive species dispersal coefficients and time-discount rate are moderate, and the problem is addressed early enough. The second part of the thesis is dedicated to the case-study of the invasion of the bay of St-Brieuc scallop fishery by an alien shellfish, the slipper-limpet. Cost-benefit analysis of the bay of Saint-Brieuc case makes use of an age-structured bioeconomic model of harvesting common scallop combined with a spatial invasion model, on which an invasion control program is studied.