Reproductive season, maturation size (LM50) and sex ratio of Metapenaeus affinis (Decapoda: Penaeidae) in Hormozgan shrimp fishing grounds, south of Iran

This study aimed to investigate the spawning season, length at first maturity (LM50) and sex ratio of Metapenaeus affinis in the shrimp fishing grounds of Hormozgan Province, west of the Persian Gulf, Iran. Samples were taken by the swept area method and trawl net with 2 cm mesh size in the cod end from January 2010 to February 2011. Results showed that the sex ratio deviated from 1:1 and female’s number were significantly higher than males. Metapenaeus affinis females had continuous spawning in all seasons but the peak spawning season was found in spring, and stage 3 of maturity was observed in all seasons. Length at maturity (LM50) for females was estimated at 27.12 mm based on carapace length. Our finding showed that LM50 of M. affinis do not change with sex ratio deviates from equal ratio.