New Zealand Journal of Marine and Freshwater Research abstracts

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Distribution of barnacle larvae in Mahurangi Harbour, North Auckland

A. T. MARTIN
B. A. FOSTER

Department of Zoology University of Auckland Private Bag, Auckland New Zealand

Abstract The naupliar stages of Balanus varie-gatus Darwin are described from laboratory-reared and field-collected specimens. In Mahurangi Harbour (36°30'S, 174°44'E), adults of B. variegatus occur in the upper reaches, Elminius modestus occurs throughout the harbour, and other coastal species of barnacles occur at the harbour entrance and outside. The plankton was sampled at 13 stations along the length of the harbour during the summer of early 1981 with a 65 nm mesh net. The larvae of B. variegatus were found in samples on 14 March (high and low tide) and 4 April (low tide). On these occasions, all stages of all barnacle larvae, and other zooplankton, were enumerated. Maximum numbers of the larvae of B. variegatus and E. modestus occurred in the middle harbour, with apparent accumulation of late stage nauplii and cyprids of the more numerous E. modestus. Maximum numbers of the nauplii of the coastal species Balanus trigonus, Chamaesipho columna, Epopella plicata, and Chamaesipho brunnea occurred at the harbour entrance, their pattern of distribution was similar to those of coastal cladocerans Penilia avi-rostris 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 is 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.

Keywords barnacles; Balanus variegatus; Elminius modestus; nauplii; estuarine plankton; larval retention; Mahurangi Harbour; distribution; description; oyster

New Zealand Journal of Marine and Freshwater Research, 1986, Vol. 20: 67-76 Received 26 April 1985; accepted 1 July 1985

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