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relationship between two variables should indeed not depend on the time periods on

which it is calculated, otherwise this would mean that the relationship is not reliable

and/or the time series are not consistent. However, we recomputed the analyses on a

common window greater than 80 years, i.e., 1868-1960, considering seven BFT time

series (Bonagia and Medo das Casas being removed since they were never synchronous

over such a period with the other BFT time series). The results computed on the

common period are highly similar to those computed on different periods, so that the

overall conclusion, i.e., the relationship with temperature, holds (see Figure 6).

Recent studies put forward that the NAO could affect Atlantic bluefin tuna,

through its impact on recruitment (Marsac, 1999; Santiago, 1998). However, Fromentin

(2002a) and the recent ICCAT workshop on environment and tuna recruitment (ICCAT,

2002) investigated the NAO/recruitment relationship, using further statistical analyses,

and found no clear connection between BFT recruitment and NAO. Our results, based

on long-term comparisons, support these last findings. The time delay between NAO

and the recruitment period can be a critical question, especially when analyses focus on

year-to-year fluctuations and are computed on short time series (which is, however, not

the case in the present study). We, thus, investigated delayed effects between Hurrell’s

NAO index and BFT time series, using a lag from 1 to 5 years (4 to 5 years

corresponding to the age-at-maturity for the East Atlantic BFT). These analyses (results

not shown) did not yield to significant relationships with the three NAO indices, so that

we may reject, from a statistical viewpoint, a possible connection between long-term

fluctuations of the BFT and NAO.

Klyashtorin (1998) put forward that the atmospheric circulation index (ACI), that

is tightly related to the excess Length Of the Day (LOD), was closely correlated with

catches of the main Atlantic and Pacific commercial pelagic fish. This study focused on

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