Physical Environment
Mangonui Harbour is a small estuarine harbour 144 hectares in size, of which 94 percent consists of mudflats. It has a short, narrowly channelled entrance between the two steep headlands, and opens out into a broad estuary. Strong tidal currents occur in the channels. The Oruaiti River enters the harbour at the southern end, and flows around the eastern side of Paewhenua Island. Much of the shoreline of the harbour has been extensively modified by reclamation, construction of causeways, and the removal of original vegetation for residential purposes. A small township is present on the western side of the harbour, close to the entrance channel. Mangonui is a commercial port, with a small wharf at Mangonui township.
Flora & Fauna
The vegetation of Mangonui harbour is typical of estuarine areas. Mangroves ( Avicennia sp. ) are present in: Butler Bay; near Tuhoatea Stream; the bay north of Bruce Farm Rd; up the Oruaiti River; to the west of Paewhenua Island; and towards the Mangonui Oruru Rd. Juncus marsh occurs to the landward side of the mangroves in all these locations, and at Tuhoatea Stream, some Muehlenbeckia marsh also. Mangroves extend about 2 km up the Oruaiti River channel, where Juncus and Leptocarpus-Typha marshes occur to landward. Further up-river, this changes to a freshwater marsh environment of Typha, Cordyline and Leptospernum (Chapman, 1978).
The Mangonui Harbour is not a major area for migrant wading birds. The dominant bird species include reef and white-faced herons, gulls, terns and pied stilts. Rare and endangered species are present in the vegetated zones: Asiatic whimbrel, spotless crake, fern bird, and banded rail (DOC, 1991).
Fish species found in the harbour are typical of most Northland estuaries, and both Pacific oysters and the native rock oyster are present.
References:
Chapman, V. J. 1978. Mangroves and salt-marshes of the Whangaroa and Whangaruru Harbours, and the Bay of Islands - A study with proposals for preservation of areas supporting the harbour ecosystem. Unpubl. report. Department of Lands and Survey.
Department of Conservation (DoC). 1991 . Coastal wetland inventory: Volume 2: Coastal wetlands north of the Kaipara Harbour catchment (Draft). Department of Conservation, Wellington.
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