Size at First Capture and Growth Parameters of the Blue Swimming Crab (Portunus pelagicus, Linnaeus 1758) in Rembang Waters, Central Java, Indonesia

Indonesia, as a maritime country, holds a significant economic value in the blue swimming crab (BSC) resources, catering to both domestic needs and international exports. Rembang Regency, Central Java Province, a key BSC production center in Indonesia, faces challenges related to the sustainability of its BSC resources. This study aimed to analyze the biological aspects of BSC, including the size at first capture, size at first maturity, and growth parameters, to inform sustainable management practices. The study was conducted from November 2023 to February 2024 in the waters of Rembang. BSC samples were collected using a random sampling method. Data collected included carapace width (mm), weight (grams), and gonad maturity stage. Analysis was performed using Microsoft Excel and FiSAT II software. A total of 786 BSC samples were obtained. The carapace width of the samples ranged from 72 to 150mm. The calculated size at first capture (Lc) for male and female BSCs was 104.1 and 104.6mm, respectively. The size at first maturity (Lm) was determined to be 116.5mm. The relationship between carapace width and weight for male and female BSCs was described by the equations W = 0.000039CW^3.096 and W = 0.00022CW^2.716, respectively. The growth equations for male and female BSCs were CWt = 161.18(1 - e^{(-1.3(t+0.076)}) and CWt = 154.88(1 - e^{(-0.64(t+0.161)}). Over the four-month study period, it was evident that BSCs of unfit size and egg-bearing females were being captured. Therefore, continuous monitoring and sustainable management practices are necessary to ensure the long-term viability of BSC resources.