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

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.