Distribution pattern and habitat shifts during ontogeny of the blue swimming crab, Portunus pelagicus (Linnaeus, 1758) (Brachyura, Portunidae)

This study determined the distribution and ontogenetic habitat shifts of Portunus pelagicus in coastal habitats in Thailand. Samples were collected by gill nets and traps, at six study sites during May 2013 and September 2014. It was found that, in the bay, the catches from both gears were significantly influenced by depth (P 0.05). For offshore, the catch was significantly influenced by season (P 0.05). The catches of berried females in the bay and in the offshore area were not influenced either by depth, or by season (P>0.05). In addition, it is proven by this study that a habitat shift during ontogeny occurs as young crabs or small-sized crabs inhabit shallow waters, and migrate to deeper water when they grow larger.