Page 10 - Sella_M_1929

It has been possible for me to accomplish this homologization of
the species of the three groups of islands, thanks to the precise
information and the photographs with which Mr. Mario Novaro of the
Canary ISo, and Major Jo Agostinho and Abbot Eo Ferreira of the Azores
have courteously favored mOo

In the Canary ISo the presence of Tho thynnus ^ although suspected
(also by De Buens Bol, de Pescas, Deoo 1922), had not yet been
demonstratedo There has not yet been any proof through hooks from
the Canary Iso , but nevertheless the photographs of Mr, Novaro indicate
its presence with all certaintyo

6) The capacity of the tuna to make great migrations is already
developed in individuals of small and medium sizes ( but already sexually
mature) " ^— • The tuna caught at Brucoli in 1926^ carrier of a hook from
North Spain, weighed 28 kgo The tuna taken in Oslofjord in 1927,
carrier of an identical hook, weighed 60 kgo

This is not in contradiction to what I said at firstj, in a
relative sense, about the probable greater sedentariness of small tuna,
especially if immature. In this case we are dealing with tuna which are
already adulto

7) The large number of hooks found in tuna, mostly in large ones,
in relation to the limited possibility which they have of getting hooked,
appears to me to be a precise indication of a condition which concerns
the fishery, and that is that the number of large tuna is relatively
limited and not infinite and thus in no way subject to influence by
the catch, as is generally held, — The fact is evidently related to
the longevity of the tuna and to its relatively slow growth, due to
which the very great number of juvenile tuna is gradually reduced by
the effects of mortality.

In this connection I can anticipate some results of a study of
mine of the growth of tuna, computed from the vertebrae of more than
lt,500 individuals, indicating in rounded figures the annual growth (by
each winter annulus completed, in individuals taken in June) in length
and in weight for the first 14 years.