In this study, the relation between the percentage of fat Eicosapentaenoic acid and Docosahexaenoic acid in Otolithes ruber fillet examined against sex maturation in spawning season, from December, 2013 to June, 2014 in Abadan area. We examined 45 fillets in 3 stages: before sexual maturity, sexual maturity and after spawning maturity. Fatty acid evaluation was done using Varian CP-3800 (GC), and the comparison between male and female was done with T-test using SPSS (Version 16). The result showed that the variation of EPA in female fishes before sexual maturity (5.62±0.38), sexual maturity (7.99±0.10) and after spawning (6.29±0.36) is significantly different (P<0.5) and the variation of this fatty acid in male fishes, before sexual maturity (5.22±0.45), sexual maturity (8.09±0.27) and after spawning (6.03±0.42) is also significantly different (P<0.5). The variation of DHA in female fishes before sexual maturity (18.48±0.41), sexual maturity (20.41±0.48) and after spawning (15.12±0.32) is significantly different (P<0.5) and the variation of this fatty acid in male fishes, before sexual maturity (16.53±1.15), sexual maturity (14.86±0.94) and after spawning (15.12±0.32) is also significantly different (P<0.5). The variation of EPA in all 3 stages between the two sexes showed no significant difference (P>0.5).