Food segregation in three species of portunid crabs

Gastric mills of 2,619 specimens of portunid crabs (Portunus pelagicus, P. sanguinolentus and Charybdis feriatus) in Tolo Harbour, Hong Kong were examined. Of these, 1,498 contained recognizable food items. A total of 34 food items were identified, 10 of which (29.4%) were common to the three crab species. The principal food items were bivalves, decapods, fish and algae. However, the percent frequency of occurrence of these food items differed significantly (ANOVA, p <0.001) among the crabs. In addition to these principal food items, differences were noted in other dietary categories: P. pelagicus and P. sanguinolentus fed on the brittle star Ophiura kinbergi, whereas P sanguinolentus and C. feriatus fed on detritus and gastropods. The diet of P. sanguinolentus was found to be more similar to C. feriatus than to P. pelagicus. Exploitation of different food items and selective feeding on common prey may reduce inter-specific competition for natural food resources and allow the three portunid crabs to co-exist in the same habitat.