The invasive alien species Pterois sp. has strongly invaded the Western Atlantic and the Caribbean Sea since the 1980s. Many studies have been set up to monitor this species. This study is the first to carry out a follow-up of these populations by capture-marking-recapture with photo-identification in a natural environment. The monitoring was carried out over a period of five months at two sites to the south of Martinique. The photo-identification technique showed a high efficiency of the method with important recapture rates (36.51% on Acropora and 43.59% on Trois Rivières). The study allowed an estimation of the population sizes and density on the sites (619 individuals per hectare on Acropora and 341 individuals per hectare on Trois Rivières). The recolonization of individuals according to their size class was also studied and showed greater movements of small individuals and a high site fidelity of larger ones.