Stock conditions and status of blue swimming crab (Portunus pelagicus) in Demak water area, northern coast of Central Java

Blue swimming crab (Portunus pelagicus) is the dominant catch in Betahwalang, Demak, and the largest export fish commodity, especially to the USA. The high demand for this crab has promoted an excessive fishing effort, causing a decrease in the crab natural stock. This study aims: (1) to investigate the biological condition of P. pelagicus in the northern coast of Central Java, and (2) to evaluate the crab stock status in this study area. The data of carapace width, body weight, Gonad Maturity Stages (GMS), and sex of the crab samples were taken from landing site or meeting point of the fishers and collectors. This study showed that the maximum carapace width of female crabs was 56-164 mm and the estimated carapace width at first maturity (Lm) was 98.2 mm. The relationships between carapace width and the body weight of the male and female crabs were positive and negative allometric growth patterns. During this assessment, the status of P. pelagicus stock indicated an 'over-exploited' condition, with an LB-SPR parameter of 19% and exploitation rate (E) was 0.66. In order to achieve sustainable use of the crab fishery, thus management measures of minimum legal size, reducing efforts, and open–close area and seasons should be implemented properly