Reproductive biology of Female frigate tuna Auxis thazard (Lacepde, 1800) caught in Coastal marine waters of Cte dIvoire
Some biological features (length-weight relationship, size at first sexual maturity, eggs variation in diameter, gonado-somatic index, hepato-somatic index, somatic condition and fecundity) and histological characteristics of frigate tuna Auxis thazard were studied. The study was carried out on 496 female fish caught in gillnets and measuring in size between 25 and 48 cm FL (centimetre Fork Length) collected from January to December 2004. The results indicated that female frigate tuna reach maturity at 29.88 cm FL. Spawning started in June while females at stage IV numbered 36.36% but it lessened in November. The peak value of gonado-somatic index, GSI (3.21 ± 0.93%), was attained in August and GSI thereafter decreased gradually from September to December. There is a direct correlation between GSI and hepato-somatic index (HSI), and an inverse correlation of these factors to the somatic condition (Kc). Absolute fecundity has linear relationship with the weights of specimens (AF = -9.3792 + 0.5485ÃÂ W) as well as with the weights of ovaries (AF = 136.11 + 13.416ÃÂ OW). Eggs frequency distribution within the maturity stages III (maturing or developing), IV (spawning), and V (post spawning) were also shown in the study.