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Methods - how we monitor estuary health

REMP

Monitored estuaries

  • southern Firth of Thames mangrove forest

    The Firth of Thames is a large compound estuary and a drowned river valley. It has a catchment area of 4194 km2 and is the primary receiving environment for the Hauraki Catchment. It is New Zealand’s largest shallow marine embayment. At its southern end several rivers (in particular the Waihou and Piako Rivers) drain into the estuary and at its northern end it opens into the Hauraki Gulf. The harbour is also used for a range of recreational activities, for commercial and recreational harvesting of seafood and aquaculture. The Firth of Thames is a site of cultural significance to Hauraki iwi.

    Miranda wading birdsThe south-western shore of the Firth of Thames is recognised as an internationally important wetland under the Ramsar Convention (one of six sites within New Zealand). The Firth of Thames Ramsar site includes around 7,800 hectares of shallow estuarine waters, intertidal mudflats, mangrove and saltmarsh, and graded shell beach ridges. It is ranked as one of New Zealand’s three most important areas for shorebirds.

    The Miranda Wildlife Refuge and nearby wetlands, which make up a significant portion of the Ramsar site, are a seasonal home to thousands of wading birds and shorebirds. From spring onwards, large numbers of migrant birds, particularly godwits and knots, begin arriving to feed. Many of these birds will have spent several weeks travelling south from breeding grounds as far away as Siberia and Alaska. In autumn these birds fly north again. The refuge is also an important site for local species, such as the pied oystercatcher, New Zealand dotterel, variable oystercatcher and black-backed gull.

    Miranda shellbankThe Firth of Thames is also an important habitat for a range of common inshore fish species, many of them of cultural, recreational and commercial value. These include snapper, kingfish, jack mackerel, red gurnard, sand flounder and yellowbelly flounder. The Firth is also a nursery area for juvenile snapper, spotted dogfish, and hammerhead shark.

    The Firth of Thames is under increasing pressure from human activities, including marine farming and the input of terrigenous sediment and nutrients due to the intensification of farming and urban development within the surrounding catchment.

Where and how we collect the data