The sexual maturity index (Lm50) serves as a crucial biological metric for determining the mesh size of fishing gear and regulating the minimum legal catch size for commercially valuable species. The morphometric sexual maturity index is widely estimated based on morphometric relationships and the relative growth of aquatic organisms and can be utilized as an alternative to the gonadal sexual maturity index in fisheries management. This study aimed to estimate Lm50 based on morphometric characteristics for kiddy shrimp (Parapenaeopsis stylifera). Samples were collected from fishing vessels operating at the Abadan, Arvandkenar, and Choeibdeh docks. In this study, the samples were first classified into juvenile and mature groups using principal component analysis (PCA). Subsequently, data were fitted to a logistic model, and the model parameters and Lm50 index were estimated using three approaches: conventional, bootstrap, and Bayesian methods. The total length of kiddy shrimp ranged from a minimum of 59.3 mm to a maximum of 126.5 mm. Among the morphometric traits analyzed in relation to total length, the carapace length was selected as the most suitable parameter for estimating Lm50. The results indicated that the sexual maturity length estimated by the three methods (conventional, bootstrap, and Bayesian) was almost identical. Furthermore, the sexual maturity length in females was higher than in males, with Lm50 values of 82.81 mm for males and 93.08 mm for females. Given that the determination of sexual maturity length in aquatic species in Iran is traditionally conducted through the observation of gonads, a process that can be time-consuming and prone to errors in identifying sexual maturity stages, the use of morphometric data for estimating maturity length offers a valuable alternative. This method is particularly significant for effective fisheries management.