Natural diet of the crab Ovalipes catharus (Crustacea, Portunidae) around central and northern New Zealand

Abstract

Foregut contents were examined of 4324 Ovalipes catharus (White 1843) collected from 11 locations in central and northern New Zealand, from November 1984 to September 1985. Of these 2572 foreguts contained recognizable food items, and a total of 72 species were identified in the diet. No significant differences were found in the relative proportions of foregut contents between males and females. Sand was an important component of the foregut contents, but was not considered part of the diet. When measured in terms of frequency of occurrence and estimated volumes (points method), Mollusca dominated the diet at 6 locations and Crustacea at 5. At all localities almost all the Mollusca eaten were small juvenile bivalves, mainly from the commercially and recreationally important genus Paphies. Callianassa filholi, O. catharus, isopods, and amphipods were important Crustacea in the diet at different localities. The diet at all localities differed significantly in the proportions of 14 dietary categories, but when 6 generalized dietary categories were considered similarities were found. O. catharus is a versatile and opportunistic predator. The possible impact of this predator on commercially important shellfish species is discussed.