New Zealand Journal of Marine and Freshwater Research abstracts

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Spatial and seasonal variation in the abundance of juvenile snapper (Pagrus auratus) in the north-western Hauraki Gulf

MALCOLM P. FRANCIS

Leigh Marine Laboratory
University of Auckland
Private Bag 92-019
Auckland, New Zealand

and

Fisheries Research Centre
MAF Fisheries
P. O. Box 297
Wellington, New Zealand

Present address: National Institute of Water & Atmospheric Research Ltd, P. O. Box 14-901, Wellington, New Zealand

Abstract  Spatial and seasonal variability in the abundance of juvenile Pagrus auratus were investigated in the north-western Hauraki Gulf using trawl tows over soft-bottom habitats. Small-scale (1 km) spatial variability was high and consistent over a period of 2.5 years. This variability was attributed to differences in micro-habitat type, with snapper preferring a mud substrate over one comprising muddy sand with a significant percentage of shell. The two micro-habitats probably result from differing current regimes, but reasons for the snapper preferences are unknown. Snapper catch rates in the Kawau Island region peaked in spring, near the time of maximum day length, and declined to low levels in autumn-winter. This seasonal cycle is thought to reflect real changes in abundance rather than variations in snapper catchability. However, no seasonal abundance cycle was found in the adjacent Whangaparaoa region, where abundance was consistently low. There was no consistent depth-related trend in abundance over the range 10-30 m, and no evidence of seasonal migration of snapper between shallow and deep water.

Keywords  snapper; Pagrus auratus; distribution; abundance; sediments

New Zealand Journal of Marine and Freshwater Research, 1995: Vol. 29: 565-579

0028-8330/95/2904-0565 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (1272K); (scanned from paper original: notes about this process)

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