Ovarian development of albacore (Thunnus alalunga Bonnaterre, 1788) in the Eastern Mediterranean Sea: a histological characterisation

Summary In order to investigate the stages of oogenesis in the albacore Thunnus alalunga, 129 females (64.0‒83.5 cm fork length‐FL) were captured by gill nets from April to August 2002–2008, in the eastern Mediterranean Sea. Based on histological examination of the ovaries, a total of seven ovarian developmental stages were identified: perinucleolar, lipid, early vitellogenesis, late vitellogenesis, migratory nucleus, pre‐hydrated and hydrated. The monthly gonadosomatic index values and the results of the histological analysis indicated that the females mature in May. The spawning stage becomes predominant in June and reaches a maximum in July. The evidence reported here indicates that the size of females at first sexual maturity was lower for the Mediterranean albacore stock than for the Pacific and Atlantic stocks.