Population dynamics and reproductive biology of Scylla serrata (Forskål, 1775) on the shores overlooking the mangrove forest of the Persian Gulf

Abstract

Size frequency distribution and reproductive biology of Scylla serrata (Forskål, 1775) collected by gill net in the tidal zone of the northern Persian Gulf were studied in May 2019 and then from November 2019 to September 2020. A biometric data of 165 mud crabs showed that males are larger compared to females. The populations of male and female crabs were dominated by adult crabs (CW > 100 mm) from winter to mid-spring (December to May). The juvenile crabs were dominant from late spring to mid-summer (May to August). The sex ratio of male:female was 3:1, with 75.2% being male. This species could spawn continuously throughout the year and its peak occurs in winter and spring. The size of the first-maturity of females and LM50% were recorded in the carapace width of 82 mm and 99.4 mm, respectively. The carapace width–weight relationship showed positive allometric growth in male crabs and negative allometric growth in female crabs with a b value calculated to be 3.43 and 2.97 for males and females, respectively.The parameters CW ∞, K, and t0 were estimated at 217 mm, 1.5 Y−1, −0.61 y−1 for males and 198 mm, 1.1 Y−1, −0.86 y−1 for females, respectively. The φ index was estimated at 4.85 in males and 4.63 in females. Total, natural, and fishing mortality rates were estimated at 3.50, 1.32, and 2.18 Y−1 for males and 1.46, 1.10, and 0.36 Y−1 for females, respectively. The exploitation ratio was calculated to be 0.62 for males and 0.24 for females.This findings state of knowledge on the population biology of mud crabs will act as a baseline to propose suitable management strategies for the S. serrata stocks on the Iranian coast as well as for future research to support the development of sustainable mud crab aquaculture and fisheries.