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Eastern Atlantic and Mediterranean bluefin tuna populations 1301
variation in catches? (3) Do these fluctuations in catches Doumenge, 1998). For these reasons and to avoid any
vary in the same manner between different locations? variations that could result from crucial changes in
Finally, we discuss possible underlying processes that fishing effort and/or catchability, we restricted the
could lead to such fluctuations. time-series analyses to data prior to 1960.
Material Data
The Mediterranean trap fishery Historically, bluefin tuna fisheries were often economi-
cally important establishments. The Royal fiscal admin-
For many years, fishers have benefitted from knowledge istration and collectors of ecclesiastical tithe and salt
of the seasonal migration of bluefin tuna, during which taxes accurately recorded their receipts. Moreover,
the fish migrate close to the coast on their way to their bankers were often involved in trap management and
spawning sites (Mather et al., 1995). To catch tuna, for several centuries kept detailed accounts of catches
fishers traditionally used either traps or beach-seines (Doumenge, 1998). For this study, we searched inten-
(Doumenge, 1998), the latter gear sometimes incorrectly sively through national and naval archives, scientific
referred to also as traps. Unlike traps, beach-seines need libraries and various Mediterranean laboratories for the
many hands to operate, so progressively they have been historical catch data. They were retrieved either from old
replaced by fixed gear. The trap system was used records published by local authorities or the clergy (e.g.
throughout the Mediterranean Sea and along the adja- Sarmiento, 1757), in books of historical analyses (e.g.
cent North Atlantic coasts, from the 14th century in Cancila, 1972), in owners’ archives (e.g. Duchy of
Sicily, the 16th century in Sardinia and Portugal, and the Medina Sidonia), or in the personal archives of passion-
19th century in Tunisia, Spain, and Morocco (Berthelot, ate and relentless scientists (e.g. Sella, Scaccini,
1869; Pavesi, 1889). The traps are fixed nets set perpen- Rodriguez-Roda).
dicular to the coast, that stop the migrating tuna and
guide them through several enclosures to the final Data were collected from beach-seine as well as trap
‘‘death room’’ (Figure 2). There, tuna are gaffed during fisheries. As the former are often mistaken for traps,
the ‘‘matanza’’. they have to be considered. However, the principle of a
beach-seine is quite different from that of a trap: it is an
Numerous authors have shown that the name and active fishing gear, requiring many hands to operate,
location of the traps has remained the same over time and very dependent on the keenness of vision of an
(e.g. Sarmiento, 1757; Parona, 1919; de Buen, 1925; observer (who issues instructions on where and when to
Sella, 1929; Anon., 1931; Rodriguez-Roda, 1964; Conte, deploy the net as tuna pass). For this reason, we did
1985; Figure 1). Migration patterns have been well not use the time-series of beach-seine catches for the
understood since the Middle Ages, so the most appro- analyses. Characteristics and origins of the different
priate locations for capturing tuna along their migration time-series are detailed in the Appendix.
routes were selected long ago. Moreover, the installa-
tions were often associated with a factory, constituting Places and periods of activity of most of the traps are
an establishment difficult to move (Dieuzeide and known from the literature (Sarmiento, 1757; Berthelot,
Novella, 1953; Doumenge, 1998). 1869; Pavesi, 1889; Parona, 1919; Cancila, 1972). The
number of active traps varied over the centuries, but
The trap was hardly modified between the 17th and during the period analysed in this paper (early 17th to
the early 20th centuries, as mentioned in the earliest mid-20th centuries), the main traps were settled and
descriptions of traps as well as recent literature active, so our data collection covered most of the fishing
(San˜ ez-Reguart, 1791–1795; Berthelot, 1869; Pavesi, activity. Nevertheless, some information is lacking
1889, for Italy; de Braganc¸a, 1899, for Portugal; because some archives were destroyed (such as the
De Fages and Ponzevera, 1908, for Tunisia; de Buen, information for the middle of the 19th century from the
1928, for Spain). However, since the beginning of the ‘‘Formica’’ and ‘‘Favignana’’ traps, which were
20th century, there have been some modifications. destroyed in a fire; Guarrasi, pers. comm.) or lost (such
Increasing coastal traffic, noise, and pollution possibly as the detailed information on Portuguese traps after
led to a reduction in trap efficiency. Nevertheless, 1930; Vasconcelos, pers. comm.). For the Spanish traps,
the modifications remained minor until the 1960s catches were a priori not recorded during the 19th
(Doumenge, 1998). Then, technical innovations, such century. There, the oldest data were recorded by the
as the replacement of the traditional nets of hemp by local aristocracy, but it lost its monopoly during the
nylon nets and, above all, the development of modern, revolution around 1815 and the fishing organization
active fishing techniques, e.g. purse-seining and long- changed completely. As a result, no catches were
lining, completely changed the context of the bluefin recorded until the early 20th century.
tuna fisheries and rendered the traps progressively
less important (Farrugio, 1981; Addis et al., 1996; Most catches (92%) were expressed as the number of
tuna caught (see Appendix). In addition, a few data
