First attempt to age yellowfin tuna, Thunnus albacares, in the Indian Ocean, based on sectioned otoliths

•The age of the first annual increment in otoliths was validated.•Age estimates ranged from 0.75 to 10.50 years.•Sex-specific growth was investigated and males grew larger than females as age older than 4 years.•Males outnumbered females at larger length of the catch (>135cm fork length). This study first attempts to investigate the age and growth of yellowfin tuna in the Indian Ocean and clarifies its sex-specific growth using sectioned otoliths. The results indicate that the assumption of annual opaque zones may be reliable and fish age at the first opaque zone formation is about 0.75 years. The age estimates cover a large range of lifespans (age estimates range from 0.75 to 10.50 years) in which the maximum age estimate shows that males (9.50 years) are older than females (6.50 years). The estimated von Bertalanffy growth curves are shown to be significantly different between sexes, while the von Bertalanffy growth parameters (L∞, k and t0) are 123.6cm, 0.846 year−1 and −0.449 years for females and 162.9cm, 0.244 year−1 and −2.139 years for males. The growth curves of both sexes are similar before 4 years, after which males start to grow larger than females. Sexual size dimorphism in growth curves occurs after mature age.