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| Ravier, Christelle; Fromentin, Jean-marc. |
| More than one hundred long-term time-series of bluefin tuna catches from the ancestral Mediterranean and Atlantic trap fisheries are used to (1) estimate historical range of BFT yields in the Mediterranean and adjacent Atlantic and (2) investigate spatial and temporal patterns of fluctuations in trap catches. Mean historical catches were around 110 000 tunas/year (± 50 000), i.e. 15 000 tons/year (∈[7 000;25 000]). Fluctuations in trap catches are of large magnitude, periods of high abundance being up to seven times higher than those of low abundance. More interesting was the occurrence of 100-year-long periodic fluctuations as well as 20-year cycles. These medium- to long-term fluctuations, representing more than 50% of the total variability in the... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Time series analyses; Abundance; Population dynamics; Long-term changes; Trapfishing. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00194/30497/28906.pdf |
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| Pusineri, Claire; Ravier, Christelle; Fromentin, Jean-marc. |
| A retrospective analysis (1951-1979) was carried out on the bluefin tuna Nordic fisheries (Norway and Germany) length and weight data distributions and compared to those of Barbate trap (Gibraltar strait, Spain) to test further Tiews’ hypothesis about the disappearance of bluefin tuna in northern seas. The cohorts were identified from weight/length distributions and compared using multivariate analyses. The results showed: (i) a synchronous ageing in the 4 fisheries, (ii) similar dominant cohorts between South Norway and Barbate in the one hand (cohorts born from 1948 to 1952) and North Norway and Germany on the other hand (cohort born in 1945), (iii) a synchronous drop (or collapse) in the catches that occurred in 1963and (iv) significant correlation... |
| Tipo: Text |
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| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00194/30500/28910.pdf |
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