Abstract:
Adult Balanus variegatus occur in the upper harbour reaches, Elminius modestus throughout the harbour, and other coastal species of barnacles at the harbour entrance and outside. Maximum numbers of the larvae of B. variegatus and E. modestus occurred in the middle harbour, with apparent accumulation of late stage nauplii an cyprids of the more numerous E. modestus. Maximum numbers of the nauplii of the coastal species B. trigonus, Chamaesipho columna, Epopella plicata and C. brunnea occurred at the harbour entrance, their pattern of distribution was similar to those of coastal cladocerans Penilia avirostris and Evadne tergestina. The only plankter with a restricted up harbour distribution was the estuarine copepod Sulcanus conflictus. The maxima of occurrence of larvae of B. variegatus down harbour from the position of the adult population are interpreted as a result of current flows and tidal oscillations, retaining the larvae within the harbour system. Such larval retention may explain why Mahurangi Harbour is a good place for oyster settlement.