Page 7 - Sella_M_1929

upper Adriatic and among the islands about the end of winter, moving in —
definite directions; there follows in June and July a pause in the
fishing, which corresponds to the removal of the tuna for reproduction}
then they reappear in August and remain until October or Novembero The
tuna which arrive in the summer remain there, in all probability through
the whole season, euid one may speak of seasonal permanence. But how
many of these same tuna will be represented in the suceeding year?
Certainly not all, for a part take other directionSc. The periods in
which this dispersal of the tuna is essentially determined are probably
linked with the two phenomena which tend to restrict the habitat of
the tuna to definite and very limited zoneso The first is related to
reproduction, the second to winteringo Following these the tuna again
takes up its, let: us say, centrifugal movement in search of food.

Without doubt then (analogously with what has been demonstrated for
other fishes) a greater sedentariness is manifested in small tuna, not
yet sexually maturo> either because they are not yet subject to reproduc-
tive migratory drives, or because they are more resistant to low
temperatures. And indeed the tuna which are captured in the winter on
all coasts (and even in the Adriatic) are small or medium-sisedo

One notes the interesting fact that the pattern described above
for the fishery of the Adriatic is repeated , with few modifications , in
all localities of the Mediterranean where tuna are fished except in the
zones of the great tuna traps. Thus in the Gulf of Lyons (see statistics of
Gourret, Ann. Mus, ffl.st. Hat,, Marseillesi RDu}.e), at Constantinople
(see statistics of the fish market in Cevedjian, Ptche et P^heries en
Turquie, Constantinople 1926), on the Mediterranean coast of Spain, etc.
everywhere there occur two pauses in the fishing, that is to say in the
preaenoe of tuna t one in the winter and the other in the reproductive
period.
The tuna, according to my observations, begins to reproduce in
the third year of age , when it has attained a weight of about 15 kg,

With regard to the reproduction of small tuna (15-30-50 kg) I will
repeat an observation which I have already made elsewhere, which is that
we are still ignorant in large part as to where are to be found the areas
of reproduction of the tuna of these sizes, because all of the large
tuna traps take almost exclusively large fish. Do the small tuna of the
Adriatic go down to spawn in the seas of Sicily? And where do the small
tuna of the Gulf of Lyons go to spawn? In Sardinian or Tunisian waters,
as Roule supposes? In reality we do not knows it may even happen that
they do not go so far, or that they reproduce in the open sea,

2) An interesting datum on the direction followed by the returning
tuna on the east coast of Sicily is furnished by the hooks from Messina.

In an investigation which I made in 1928 in these tuna fisheries
(S. Fanagia, Marzamemi, C. Passero, etco), I was able to ascertain that
numerous hooks from Messina (hooks which are unmistakable because of their