and those of Cyrenaica, Tunisia, and Sardinia was established, these 

 differences of salinity could be attributed to different adaptations, 

 in relation to differences of race, but once the possibility is 

 recognized that the same tuna, as an individual, may move indifferently 

 between these various points, it is necessary to come to the conclusion 

 that its movements are not noticeably influenced by salinity, within 

 the very broad limits specified above,, 



It does not seem to me, therefore, that the theory of Roule can 

 be maintained, according to which the tuna, even though non-spawning, 

 although with less strictness than when ripe for spawning, tends to seek 

 and remain in the most saline waterso 



Even the strict stenohalinity and stenothermy of the ripe tuna, 

 furthermore, in the sense maintained by Roule of a concentration of tuna 

 on spawning grounds with maximum salinity and temperature (even if con- 

 sidered as limited to certain basins, for generalizing one falls into 

 an absurdity), has not found confirmation in numerous salinity determina- 

 tions (over SOO) made by us in the past 2 years from samples which we 

 had collected on 12 tuna fishing grounds in Sardinia, Calabria, Sicilia, 

 P\iglia, and Tripolitania, nor in observations of temperatures. 



Therefore it can be concluded at the present time, and thus only 

 provisionally (because to arrive at definitive conclusions it is 

 necessary to be able to compare the conditions of several years), that 

 the small and medium mature tuna (Calabria, Tripolitania) and the large 

 ones (Favignana and the groun of tuna fisheries of Carloforte) have 

 somewhat different habits5/and that the larger tuna would prefer waters 

 relatively less saline and less warmo High salinities do not appear to 

 be favorable to ripe tuna, and this would be one of the causes of the 

 lack of tuna spawning grounds in the eastern Mediterranean^ One should 

 speak of seeking, not the most saline and the warmest waters, but waters 

 having definite characteristics., 



9) Is the balance between the tuna of the Atlantic and the 

 Mediterranean influenced by the transportation of eggs and 'larvae 

 through the Strait of Gibraltar? 



Roulei2/ supposes that if a passage of tuna through the Strait 

 does occur, it must happen through the passive transport of larvae from 

 the Mediterranean to the Atlantic in the deep outflowing current, these 

 seas still remaining practically independent with regard to the adult 



w 



Even -fclie season can be somewhat different, thus in Tunisia ajid 

 Tripolitania the tuna fisheries made their catch latere 



Cons, Int. Bxplo de la Mer, Rapp„ et Po V, , vol, 34| Office Sc, et 

 Techn, PStehes Mar, , Notes et Memo , Noo 39o 



