Dietary partitioning by two sympatric fish species, red cod (Pseudophycis bachus) and sea perch (Helicolenus percoides), on Chatham Rise, New Zealand

Abstract

The diets of red cod Pseudophycis bachus and sea perch Helicolenus percoides were determined from examination of stomach contents of 246 and 494 specimens, respectively, sampled by bottom trawl on Chatham Rise to the east of South Island, New Zealand. The distributions of both species on Chatham Rise overlapped geographically and by depth; the entire P. bachus distribution was encompassed by the H. percoides distribution. The diets of both species were dominated by crustaceans, but fish was also an important dietary component for P. bachus, while pelagic tunicates were important for H. percoides. Despite the overlap in spatial distribution, P. bachus and H. percoides had distinct diets with non-significant overlap, which will markedly reduce resource competition between these two species. The most important crustacean prey were Galatheidae (Munida sp.) and the pandalid shrimp Notopandalus magnoculus in P. bachus, and two-spined crab (Pycnoplax victoriensis) and isopods in H. percoides. Within-species variation in diet was influenced by predator location and ontogeny. The main ontogenetic shifts in diet were from small shrimps to larger fish prey for P. bachus, and from small crustaceans (mysids and galatheids) to larger crustaceans (scampi and crabs) for H. percoides.

Keywords:

• Trophic relationships
• spatial
• niche

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

Thanks to Amelia Connell and Darren Stevens for assistance in prey identification, and three anonymous reviewers for constructive comments on the draft manuscript. This work was part-funded by the New Zealand Ministry of Fisheries projects ZBD2004-02 and NIWA project CF113511. Thanks to the staff on the RV Tangaroa for collection of the samples.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark