For the past four years, blue crabs have proliferated in the lagoons of Occitania, southern France, to the great displeasure of fishermen who have seen the number of marine species living in the ponds decrease drastically. This crab is one of the 100 most invasive species in the Mediterranean. In the pond of Canet-Saint-Nazaire, several thousand crabs are caught every day. IMAGES AND SOUNDBITES