Reproductive biology and histological characteristics of female little tunny Euthynnus alletteratus (Rafinesque, ۱۸۱۰) caught on continental shelf of Côte d’Ivoire

Some females little tunny (n=۳۹۵) caught in gillnets and measuring in size from ۳۵ to ۷۶ cm FL (centimetre Fork Length) were sampled from January to December ۲۰۰۴ to study 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) along with histological characteristics of the reproduction process in this species. Female E. alletteratus reached maturity at ۴۲.۵۴ cm FL. Maturity stage distribution and gonado-somatic index (GSI) revealed that spawning period extended from May to October, with a peak value of GSI attained in August. There is a direct correlation between GSI and hepato-somatic index (HSI), and an inverse correlation of these factors to the somatic condition (Kc). The absolute fecundity has linear relationship with the weights of specimens and weights of ovaries. Yet, curvilinear relationship was found between the absolute fecundity and sizes of females. Eggs count in ovaries at spawning (IV) and post spawning (V) stages revealed bimodal size classes, while ovaries at maturing stage III showed unique modal-egg-frequency distribution.Some females little tunny (n=۳۹۵) caught in gillnets and measuring in size from ۳۵ to ۷۶ cm FL (centimetre Fork Length) were sampled from January to December ۲۰۰۴ to study 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) along with histological characteristics of the reproduction process in this species. Female E. alletteratus reached maturity at ۴۲.۵۴ cm FL. Maturity stage distribution and gonado-somatic index (GSI) revealed that spawning period extended from May to October, with a peak value of GSI attained in August. There is a direct correlation between GSI and hepato-somatic index (HSI), and an inverse correlation of these factors to the somatic condition (Kc). The absolute fecundity has linear relationship with the weights of specimens and weights of ovaries. Yet, curvilinear relationship was found between the absolute fecundity and sizes of females. Eggs count in ovaries at spawning (IV) and post spawning (V) stages revealed bimodal size classes, while ovaries at maturing stage III showed unique modal-egg-frequency distribution.

Keywords:

Absolute fecundity , Gonado-somatic index , Hepato-somatic index , Little tunny , Somatic condition