Blue swimming crab Portunus pelagicus, Linnaeus, 1758 in Pare Pare Bay, South Sulawesi, Indonesia: Study of reproduction and breeding potential

The blue swimming crab ( Portunus pelagicus ) fishery is an essential fishery in the Indo-Pacific region, including Indonesia, but P. pelagicus populations face over-exploitation. This study investigates the sex ratio and reproductive dynamics of P. pelagicus harvested in Pare Pare Bay, South Sulawesi, Indonesia. From July 2023 to June 2024, we conducted monthly surveys at a crab landing site for a local, small-scale fishery. A total of 5777 P. pelagicus were collected and measured to assess sex ratio, spawning season, fecundity, and egg diameter. Environmental data (salinity, water temperature, dissolved oxygen, and pH) were collected monthly at four stations in the Bay. They were compared using correlation analyses to the sex ratio and proportion of ovigerous females. Our results indicate that male crabs were consistently more abundant than females at a ratio of 1.4:1, and month-to-month changes in the sex ratio were positively correlated with warmer water temperatures. For female crabs captured in the Bay, 20 % were ovigerous, peaking at 31 % in March. Larger crabs had significantly higher fecundity and egg diameter that varied from 280 to 328 µm. This study provides baseline information on seasonal variation in sex ratio and reproduction to inform the development of aquaculture and conservation efforts.