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MATERIALS

The bluefin tuna trap catches

An intensive investigation through archives and historical literature allowed us to

collect more than a hundred time series of catches from the ancestral Mediterranean and

Atlantic trap fishery (for more details, see Ravier and Fromentin, 2001). Traps are

passive and fixed gears that were used from the Middle Age in Italy and Portugal, and

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from the early 19 century in Tunisia, Spain and Morocco. They were hardly modified

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and their numbers and locations varied slightly until the mid-20 century (Rodriguez-
Roda, 1964; Sella, 1929). This suggests that fishing effort is likely to have little varied

over several centuries. The long-term fluctuations in trap catches represented the main

source of variance and were statistically synchronous all along the western

Mediterranean and the Atlantic coasts of Spain and Portugal, so that they could be

considered as a good proxy of variations in BFT population migrating each year into the

Mediterranean to spawn (Ravier and Fromentin, 2001, Fig. 1).

Because the time series of trap catches mainly exhibited low frequencies, we

based the present study on those displaying at least a period of more than 80 contiguous

years without missing values and a total percentage of missing values over the whole

time series < 10%, i.e. a pool of 9 time series (see Table 1). The longest time series

came from the Sicilian traps “Favignana”, “Formica” and “Bonagia” and spread over 4

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centuries (17 to 20 ), but included gaps (Table 1, Figure 2). Records of trap catches
from Sardinia (“Saline”, “Porto Paglia”, “Porto Scuso”, “Isola Piana”, Table 1, Figure

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2) and Tunisia (“Sidi Daoud”) went back to the 19 century (1825 and 1863

respectively) and those from Portugal (“Medo das Casas”) started at the beginning of

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the 19 century and then spread from 1852 to 1933 (Table 1, Figure 2).

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