ABSTRACT. – Considered by some researchers to be invasive in some parts of Europe, the freshwater shrimp Atyaephyra desmarestii has been poorly studied in Morocco. This study reports from the survey of 90 stations situated in the Moulouya watershed and in the Oriental region of the country. Twenty-nine stations, visited three times between 2014 and 2016, reveal the presence of the freshwater shrimp. Twenty-three stations among the 29 showed significant fluctuations in the abundance of the crustacean in time and space. The analysis of the data collected from these 23 stations show that it occupies a large range of habitats, and exhibits a great plasticity against water quality. It concludes that in the watercourses of the Moulouya watershed (even slightly oxygenated), the main factor limiting the geographical distribution of A. desmarestii is the velocity of the water current.