Food of predatory demersal fish in Hauraki Gulf

Abstract

In 1965–66, the feeding relationships of snapper Chrysophrys auratus (Forster), trevally Caranx lutescens Richardson, red gurnard Chelidonichthys kumu Lesson and Garnot, horse mackerel Trachurus novaezelandiae Richardson, eagle ray Holorhinus tenuicaudatus (Hector) and John dory Zeus japonicus Cuvier and Valenciennes were examined at two specific sampling areas (“combined” and Kawau stations) in inner Hauraki Gulf and more generally throughout the entire Gulf and along the northwestern edge of the Bay of Plenty. An analysis at specific sampling areas, made by calculating the indices of competitive independence, indicated that interspecific competition occurred rarely and relatively mildly. The general analysis throughout the study region, made by comparing the diet compositions of the predatory fish species, showed that competition was again largely avoided by differences in food preferences and feeding habits. Snapper had the greatest diversity of diet and the smallest feeding overlap; these facts may explain why the relative numbers of snapper are greater than those of any other predatory demersal fish in the region.