Page 5 - DiNatale2010

How these variations can be interpreted is not easy. In some cases there was an export of know-how from some
countries to others, in other cases they were possibly caused by a different availability of the bluefin tuna in
some coastal areas, either in a positive or negative sense.

Due to the fact that tuna farms were real industries, the economic factors could be also a part of these changes
over time, but a much more in-depth and specific analysis is necessary to better and more properly explore the
data, while detailed information is not available for most of the factories and it is often preserved in hand-written
old logbooks, sitting in unknown places or archives (in some cases, these archives are in local churches, because
there was the tradition to provide a quota of the income to the local church, as a sign of devotion). In other cases,
economic information can be found in official publications dealing with annual permits or annual catch reports.

At the same time, it is important to note the stability reported in Malta, possibly as the result of no relevant
changes in this key area in the central Mediterranean Sea, and in Turkey, where the number of the many tuna
traps was stable over these 20 years. This last situation is particularly relevant, because it is strictly related to the
migration of bluefin tuna from the Black Sea to the Aegean Sea and vice versa, a situation which had completely
changed in the last part of the 20th century (Devedian, 1926; Iyigungor, 1957; Karakulak, 2000; Mert et al.,
2000; Sarà, 1963). At the same time, the relevant number of Turkish traps at the beginning of the 20th century
confirms the massive presence of bluefin tuna in this extreme Eastern Mediterranean area, supporting the
economy of 26 factories.

Tuna traps were often very concentrated in some coastal areas, where the passage of bluefin tuna was more
abundant or common and the map provided by Parona (1919) is able to give a clear overview of the distribution
of tuna traps along the coasts (see Figures 4a and 4b).

From the maps provided both by Pavesi (1889) and Parona (1919), it is very clear that the areas having the
highest concentration of tuna traps were those in the central Mediterranean Sea, with other peaks at the two
geographic extremes, close to the Strait of Gibraltar and the Strait of Bosphorus.

The tuna trap fishery, according to Avolio (1805), was carried out in the Mediterranean from March to June in
the 18th century. This period is slightly different from the actual one, which is usually from May to June. The
fishing season is broader if the tuna traps located in the Atlantic are taken into account, because in this area the
fishery is carried out from April to August.

Actually, there are only a few traps still active and not all of them are fishing every year. Seventeen traps are
active in Morocco, all in the Atlantic (Abid & Idrissi, 2009) but with 7 new traps activated since 2007, five are in
Italy (only three, all located in Sardinia, were fishing in 2009), four are in Spain (all in the Atlantic) and one is in
Libya, while others in various places still have their nets and equipment but are no longer active.

The tuna trap fishery has very high cultural and socio-economic value and some countries had already officially
recognised it. The buildings forming the land structure of each tuna trap have very high historical and
architectural value, sometimes also recognised by the UNESCO. The huge staffs working in each tuna trap and
the Rais (the specialist in charge of heading and driving the fishing activities) are all highly specialised, and they
cannot be easily replaced and their knowledge is a patrimony to be preserved, as well as for the other aspects of
the tuna trap fishery.

The most important point that is necessary to discuss in this paper is why this fishing activity had so many
changes over time and in which way these can help in better understanding the current problems of the bluefin
tuna. It is sufficiently clear that several changes in the tuna trap fishery are strictly related to problems which are
far from the total abundance of the biomass in the area (Mediterranean and Atlantic together) and this can
provide arguments for our discussion.

The complexity of the various situations needs to restrict the analysis to a few points, which appear particularly
interesting: the lower availability of bluefin tuna along most of the coasts and the total disappearance of the
Turkish traps in the Bosphorus in the last quarter of the 20th century.

The first point is maybe the most difficult to examine, because it concerns mostly the alteration of the coastal
environment over time. The increasing number of new, large harbours in all countries, the incredible increment
in the inhabitants along the coast, the concentration of several production and industrial activities in coastal areas
and the modification of the quality and quantity of river inputs to the sea had progressively caused many changes
in the chemical and physical parameters of the sea water in coastal areas.

1008