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Size and age at sexual maturity of female bluefin tuna (Thunnus thynnus L. 1758) from the Mediterranean Sea


Author's address: Gregorio De Metrio, Department of Animal Health and Well-being, University of Bari, S.P. per Casamassima km. 3, I-70010 Valenzano (BA), Italy.


The ovaries of 501 female eastern Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1758) captured in the Mediterranean Sea from May to September between 1998 and 2004 were analysed histologically. Body size at median sexual maturity (L50) was 103.6 cm fork length (FL), while 100% maturity was reached above 135 cm FL. The age analysis, based on the count of the translucent zones of the first spiniform ray of the first dorsal fin, showed that most of the specimens with FL = L50 were 3 years old while 100% maturity was reached between 4 to 5 years. The reported evidence indicates that for the eastern Atlantic bluefin tuna stock, the size and age of first sexual maturity of females was lower than in the western Atlantic stock.