The determination of Mediterranean Salmonidae has been possible because of morphological and morphometrical studies and immunological and biochemical methods. It is evident that the 'sea trouts' belong to the species S. trutta fario and S. gairdneri irideus. These trouts have been acclimatized naturally to marine life. Experimental tests were undertaken in the laboratory, then in natural medium, to study the possibilities of trout acclimatization in sea water. They have confirmed the great adaptation qualities of these fishes to often extreme conditions. In the experiments undertaken in variable conditions, the influence of temperature and oxygen were exactly specified. Following these experiments, and other experiments realized in France and in other countries, it is evident that trout rearing in sea water is possible, if one uses well oxygenated sea water and fresh water and if one applies the techniques to the selected site, settling them in function of the behaviour of the fishes.