ABSTRACT
Anadromous fi shes are those among diadromous fi shes (truly migratory fi shes which migrate between the sea and freshwater) who spend most of their lives in the sea and migrate to freshwater to breed (Myers 1949). These movements between habitats occur at a specifi c timing in the ontogeny and concern either part or all individuals of a population (Fontaine 1975). But who are these anadromous fi sh? According to several authors, the number of anadromous species is not yet fi xed and is probably underestimated, and estimates varied between 109 (McDowall 1988) and 175 anadromous species (Riede 2004), which corresponds to 23 and 31 families around the world, respectively. Considering the 33,059 fi sh species described around the world (Eschmeyer and Fong 2014), anadromous species represents about 0.5% of the whole fi sh species. They occur among the class of Actinopterygii (among 28 family over 491) and Cephalaspidorphii (among the three families of the order Petromyzontiformes: Petromyzontidae, Geotriidae and Mordaciidae). No anadromous species are mentioned in the literature in the following classes: Myxini, Elasmobranchii, Holocephali and Sarcopterygii.
