Population characteristics such as population structure, growth, mortality, and size at sexual maturity of P. gravieri inhabiting warm temperate waters were investigated using size-frequency distribution data (January 1999 to December 2000). Sexual differences for carapace length/total weight and carapace length and total length were statistically significant in the intercept of the regressions in the former relationship and the slope in the latter, respectively. Population size based on size-frequency distribution between female and male and between two years were described. Population density was high in March and April during two years of sampling. Sex ratio was biased toward females for most of the months sampled. Growth was continuous and seasonally oscillated throughout the year. Adult females were larger and grew faster than males. The von Bertalanffy growth parameters for two-year pooled samples between females and males were estimated as L_∞ = 23.20, K = 0.8, C = 0.4, WP = 0.1, Rn = 0.269, t₀ = −0.016 (females); L_∞ = 18.59, K = 0.704, C = 1.00, WP = 0.2, Rn = 0.326, t₀ = −0.023 (males), respectively. Instantaneous total mortality (Z) for two-year pooled samples were estimated by the equation y = −3.92x 11.89 (n = 10, r = 0.920) for females and y = −2.41x 10.57 (n = 9, r = 0.976) for males, respectively; sexual maturity was estimated to be at 7.89 mmCL (carapace length).