The blue swimming crab (Portunus pelagicus) is a valuable commercial species widespread across tropical coastal waters of the western Indian Ocean and eastern Pacific. In 2020, fishery trends showed that blue swimming crab (BSC) catches remained at their highest levels. Notably, the demand for seafood is increasing, while natural marine resources are decreasing, due to overexploitation and habitat destruction, with the BSC being one of the species under threat in many Asian countries. Culture development of the BSC is one potential and promising long-term solution to cope with this problem. This study examined the optimization of stocking density in grow-out ponds, where density affected growth, survival, and economic feasibility. Identifying an optimal density was essential to maximize production efficiency, and profitability.
The study was conducted at the Klongwan Fisheries Research Station in Thailand from April 2022 to March 2024. Juvenile BSC were reared in a 1,600 m² grow-out pond at three stocking densities: low (1 crab/m²), medium (3 crabs/m²), and high (5 crabs/m²). BSC were fed an artificial shrimp feed (No. 4S; pellet size 3.5 mm, 38% protein) at 5% of body weight per day, with feedings twice daily at 0900 and 1700 hours. Over a 90-day period, survival (SR), weight gain (WG) growth rates , and feed conversion ratio (FCR) were monitored, along with some economic metrics, including total revenue (TR), and payback period (PBP).
Results demonstrated that stocking density significantly impacted the SR, growth performance, and revenue in BSC cultivation. As density increased, SR declined, with low- and medium-density groups achieving better overall outcomes compared to high-density ponds. Higher densities resulted in lower growth rates (WG, ADG, and SGR), reduced TR , and an elevated FCR (Table 1). The stocking densities of 1 and 3 crabs/m2 were more suitable for BSC cultivation compared to 5 crabs/m2 . Economically, the PBP for these two densities were 3.9 and 4.2 years, respectively. To promote sustainable commercial cultivation, further research is recommended to develop strategies for increasing production or reducing cultivation costs at these densities , thereby enabling a faster return on investment.