Comparative Analysis of Growth Patterns and Sexual Dimorphism of Scylla paramamosain in Pond Culture

To investigate the growth patterns and sexual differences in pond-cultured mud crabs (Scylla paramamosain), this study measured eight growth patterns in pond-cultured S. paramamosain aged 1 to 5 months, including internal carapace width (ICW), abdomen width (AW), body height (BH), carapace length (CL), propodus length (PL), merus length (ML), first periopod merus length (1PML), and body weight (BW), with measurements taken monthly. The growth patterns for females, males, and a mixed-sex group were fitted using the following three growth curve models: Logistic, Gompertz, and von Bertalanffy. The fitting results indicate that the optimal growth model for male S. paramamosain is the Logistic model, while the optimal growth model for female S. paramamosain is the von Bertalanffy model. The predicted growth inflection points and inflection weight for male S. paramamosain are 3.15 months and 155.00 g, respectively; for female S. paramamosain, the predicted growth inflection point and inflection weight are 4.25 months and 228.71 g, respectively; and for mixed-sex S. paramamosain, the growth inflection point and inflection weight are 3.22 months and 151.80 g, respectively. Males achieve a rapid growth period earlier (at 3–4 months of age) than females, with the weight of male crabs significantly greater than that of females at four months of age (p < 0.05). Males exhibit slow weight gain from the fourth to the fifth month, while females demonstrate a rapid weight gain rate during the same period. These results provided a theoretical basis and reference for the refined pond culture of S. paramamosain.