Biology of little tunny Euthynnus alletteratus in the Gulf of Gabes, Southern Tunisia (Central Mediterranean Sea)

Biological features known as sex-ratio, Gonad-Somatic Index (GSI), Hepatic-Somatic Index (HSI) and size at first sexual maturity, and the length-weight relationships (LWR) were studied in little tunny, Euthynnus alletteratus, caught in the Gulf of Gabes (Southern Tunisia). A total of 397 little tunny (244 females and 153 males) were analysed. Fish length ranged between 36.7 and 97.8 cm, average 52.29 ± 5.87 cm. Samples were monthly fished from January 2008 to December 2009. Sixty one percent of the specimens caught were females. The high GSI suggest that the spawning period runs from June to September. Fish in spawning condition are to be observed in August since GSI reaches the peak in July. Negative allometry was found in little tunny. Fork length at first sexual maturity in males (42.8 cm) was smaller than in females (44.8 cm).