Batch fecundity of the swimming crab Portunus trituberculatus (Brachyura: Portunidae)

We assessed batch fecundity of the swimming cab Portunus trituberculatus for the purpose of seed production. Oocyte number and number and body size of first zoeas were examined for females collected from natural habitats in the Seto Inland Sea of Japan. The relationships between carapace width (CW) of females and batch fecundity were analyzed using a power function. Oocyte number was examined for the overwintering females. Size and number of first zoeas were determined for ovigerous females collected from May to August. Oocyte number increased with increasing female body size and predicted estimates ranged between 0.8 and 4.5 million for CW of 130–240 mm. Size of first zoeas (distance between tips of dorsal and rostral spines of the carapace) ranged between 1.22 and 1.62 mm and tended to linearly decrease with advancing hatching date, i.e., increasing hatching temperatures. Number of first zoeas increased with female body size and showed no fluctuation throughout the breeding season in females of the same size. Predicted numbers of first zoeas ranged between 0.7 and 3.8 million for CW of 130–240 mm. Number of first zoeas being less than the oocyte number for females of the same size, it is suggested that egg loss occurred from oviposition to hatching.