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16 Mar Ecol Prog Ser 359: 11–23, 2008

RESULTS and Formica), Sardinia (Saline, Porto Paglia,
Portoscuso, Isola Piana) and Tunisia (Sidi Daoud)
Significant cycles in bluefin tuna time series (Fig. 3). These time series were selected from an
extensive dataset of more than 100 time series, as
Time series they displayed a common period of 83 contiguous
years (1878 to 1960) without missing values. They
An extensive description of the whole dataset can also displayed synchronous long-term and short-term
be found in Ravier & Fromentin (2001, 2004). These fluctuations, and they thus constituted good exam-
data consist of 7 time series of trap catches from ples for comparing various null models (Ravier &
various Mediterranean locations: Sicily (Favignana Fromentin 2001, Royer & Fromentin 2006). We used
the beta surrogates to test whether or not the
fluctuations detected in these time series were
artefacts of the autocorrelation structure of the time
series. The results were then compared to those
obtained using Type 1 surrogates (Fourier surro-
gates), AR[1] and white noise, in order to assess their
relevance.

Fig. 3. Mediterranean Sea and geographic origin (1 to 7) of the Bluefin tuna trap time series. Adapted from Ravier & Fromentin
(2004)