population. Basing his belief on the established fact that larval tuna 

 are unknown in the zones of the fisheries, he supposes that the larvae 

 are negatively phototropic and that they go very deep to the lower strata. 



It is a fact that even the Thor succeeded in its cruises in 

 capturing only a very limited number (13) of juvenile stages^ which 

 Ehrenbaum (Danish Ocean. Exp., vol. II, 1924), who described this 

 material, attributed only doubtfully to the tuna (and in truth, in Ariew 

 of material in my possession which I have already described in part 

 elsewhere, see Rend. R. Acco Lincei, 1924, I do not believe that they 

 are tuna)o 



As a matter of fact we have taken in the Strait of Messina 

 repeatedly, in different years, thousands and thousands of larval tuna 

 on the surface with lightsli/ and in the cruise of the Ciclope in June 

 of 1913 along the north and east coasts of Sicily we took with plankton 

 nets several dozen juvenile stages of tuna at different depths. 



As for the tuna's being negatively phototropic, I mast record the 

 fact that the catches mentioned above, made in the Strait of Messina, 

 have demonstrated that the juvenile stages of the tuna react violently, 

 in a^ positive sense , to artificial light to such an extent that they 

 have been taken with a simple dipnet under the light. This instinct is 

 later modified gradually and profoundly with age . Tuna barely past the 

 larval stage move very swiftly and therefore a special skill is necessary 

 for their capture. In any case the short period of incubation of the 

 tuna's eggs, and the rapidity with which the larvae and the juvenile 

 forms not only grow but also acquire independence of movement certainly 

 preclude the possibility of the occurrence of a passive movement of tuna 

 from the major centers of reproduction of the Mediterranean (Sardinia, 

 Sicily, Tunisia, and Tripolitania) to the Atlantic At the age of 15 

 days the tuna may already be considered an active fish^ 



The situation is different in the zone adjacent to the Strait of 

 Gibraltar, where on the Atlantic side we have a very important spawning 

 area, while on the Mediterranean side there are no reports of any such, 

 or at least there are no tuna fisheries. De Bu'^^n has already pointed 

 out the possibility of the passage of eggs and larvae, emphasizing that 

 iti the region just this side of the Strait, between Ceuta and Melilla, 

 great quantities of juvenile tuna are collected; I note, however, that 

 the tuna of which he speaks are already fish of some size, from several 

 hundred grams to several kilograms, that is, perfectly active and even 

 capable of having migrated spontaneously. Tuna hatched in June already 

 weigh 300-500 grams in September and are already taken on trolling lines. 



w 



These collections were ipade for me by Prof. Sanzo, to whom I 

 am indebted for much assistance in these researcheso 



