The habitat of the tuna appears to be regulated in large part by 

 the Gulf Stream ; in fact this coincides (even in the United States and" 

 Canada, where the tuna is lacking in the part subject to the cold Labrador 

 current), with the area in which the current of the Gulf makes its 

 influence felt. Evidently the presence of tuna north of Norway, at 

 the polar limits, can only be explained thus. 



We can, to a certain extent, evaluate even the speed at which the 

 tuna are capable of dispersing, and can find confirmation that the fish 

 possess physical powers which render them able to make these great 

 seasonal wanderings, in the following fact. At Cristiansund in Norway, 

 where the arrival of the tuna is now checked by capable fishermen and 

 observers, the first tuna arrive in the first week of July, exceptionally 

 at the end of June. I have information from private sources to the 

 effect that Mr., Hanson caught a tuna which still showed traces of recent 

 spawning., 



These tuna certainly come from the southern zones of reproduction," 

 of which the nearest is in Spanish waters or, in any case, not appreciably 

 farther north. The tuna never spawns before June. One can , then , 

 calculate that in less than one month the tu na makes a journey , certainly 

 not direct , from the south of Spain to Norway^ 



Interesting, too, is the observation of Hanson (Cfro HHeg, in II 

 Risveglio della Pesca , no 8, 1927, Milano), that in Norway regularly the 

 large tuna appear first and then the small ones, with a lag of about 3 

 weekSo I consider this to be precisely in accord with the fact which I 

 have 'ascertained in the Italian and Tripolitanian fisheries, that the 

 large tuna ( around 100 kg or more ) matu re and release their sexual 

 products before the small tuna (15-30-50 kg); and actually the spawning 

 of the large tuna is finished at the beginning of July, while that of 

 the small tuna continues to the end of that month or a little longer, 

 in the fishery for returning tunao Also the disagreement noted above 

 between the classical spawning season of the tuna (May-June) and the 

 period in which actually the greater part of the tuna move off from the 

 northern coasts of the Mediterranean (June-July) results from this fact. 



Among the direct proofs, then, of the movement of tuna from north 

 to south for reproductive purposes in the Mediterranean, it seems to me 

 that the most suggestive is that of the four leads from Constantinople, 

 found in a single fishing season (1927) and in different individuals, 

 in tuna from the fishery of El Mongar near Bengazi in Cyrenaica, which 

 cannot be explained except by the arrival en masse in Cyrenaica of 

 individuals coming from the Sea of Marmara and the BosphoruSo 



Proposal to the Congress 



l) For the study of the migrations of the tuna, I propose that in 

 agreement with our Spanish colleagues provisions be made for the marking 

 of a_ certain number of hooks of the Spanish type for fishing for tuna and 



17 



