The reproductive biology of blue swimming crab Portunus pelagicus in Southeast Sulawesi waters, Indonesia

Blue swimming crabs (BSC) (Portunus pelagicus) fisheries in Southeast Sulawesi waters have experiencing huge pressure, however studies on their reproductive biology were limited. The objective of the study was to find out the growth model, size at the first maturity, fecundity, and sex ratio disparity of BSC. The samples were collected monthly during June 2014 - April 2015 using gillnets, crab pots or hand-picking. Berried females were collected for fecundity (F) analysis. Relationship between weight (W) and carapace width (CW) were analyzed using a simple linear regression. The CW size of the first maturity was pointed out at 50% of frequency cumulative (CW₅₀), while relationship between F and CW was analyzed following F = a*CW^_b. Sex ratio of both sexes was tested using the Chi-square (α = 0.05). The result shows growth model of both sexes was “allometric” (b < 3) following equation of W = -1.6181 + 0.0224*CW for males and W = -1.7909 + 0.0238*CW for female. The relationship between F and CW was F = 80.443e^0.0236 CW (r = 0.7679). This organism produces high fecundity as its biology reproductive strategy to maintain its population. Males and females attaine the first maturity at CW₅₀ of 11.957 cm and 10.802 cm, respectively. The sex ratio generally females preponderate over males, however, the Chi-square test was not significantly different. Factors affecting sex ratio disparity were mainly locations (water quality), migration and distribution patterns according to sex, sampling method, gears catchability, mortality and growth, reproduction activities, and CW sizes.