The Implementation of Size Limit Regulation on the Swimming Blue Crab (Portunus pelagicus) Catches in Indonesia: To Maintain Resource Sustainability

   The policy regulating the minimum size of crabs (Portunus spp.) that can be caught in Indonesia has not yet been thoroughly assessed in various regions, which is crucial for promoting sustainable fishing and protecting the marine environment. In Kendal waters, Central Java—a fishing area frequently visited by local fishermen—detailed information on the captured crabs, including species, sex distribution, size, and the proportion of crabs meeting the catch criteria, is lacking. Understanding the natural stock’s genetic information can help policymakers design fishing operations and conservation management policies to maintain genetic diversity. The study was conducted from September to October 2023, with crab samples collected from collapsible traps at 10 fishing grounds in Kendal waters. The crabs were identified, measured for carapace width, weighed, and sexed. Descriptive analysis was used to understand the distribution of carapace width and weight at the study sites. Simple regression analysis was applied to assess correlations between variables. The findings revealed that the crabs captured in Kendal waters were predominantly the blue swimming crabs (Portunus pelagicus) and crucifix crabs (Charybdis feriata), with the blue swimming crabs accounting for 87.79%. The observations indicated an imbalance in the sex ratio, and the growth of crabs in Kendal waters was positively allometric—meaning the body weight grew at a faster rate than the carapace width. The size distribution of crabs was generally smaller during the east monsoon, and the first-caught crabs were larger than the legal size requirement. Most of the captured crabs (90%) fell within the eligible size classification.