Ontogenetic diet shifts in snapper (Pagrus auratus: Sparidae) within a New Zealand estuary

Abstract

The diet of the sparid fish Pagrus auratus (snapper) was examined within the Mahurangi Harbour in north-eastern New Zealand. Ontogenetic shifts occurred in diet. Individuals <20 mm (fork length) consumed planktonic copepods, with a shift at 20 mm to benthic copepods, mysid and caridean shrimps and polychaetes. Snapper >100 mm consumed brachyuran crabs, caridean shrimps, bivalves, polychaetes and hermit crabs, with individuals >300 mm also able to consume harder shelled molluscs and bivalves. The stomach contents of juvenile snapper (10–100 mm) sampled across habitats of sand, shell hash, horse mussels and subtidal mud showed differences in major prey taxa; however, these differences were small. This may be advantageous for juveniles, which can then select a habitat for other qualities. A comparison with eight other studies on the diet of snapper from coastal areas showed crustaceans were consistently the most highly ranked major taxon; however, differences among other major taxa were relatively minor.