Freshwater

A regular newsletter with updates on New Zealand's water resources and NIWA's latest freshwater research.

These guidelines outline a recommended minimum set of methods for a community group interested in following habitat changes in an estuary.

Where an online version is not available, a PDF is provided. Use your browser’s Back button to return to this page.
Bell, R.; Green, M.; Hume, T.; Gorman, R. (2000). What regulates sedimentation in estuaries? Water & Atmosphere 8(4): 13–16.
Davies-Colley, R.; Nagels, J.; Donnison, A.; Muirhead, R. (2004). Flood flushing of bugs in agricultural streams. Water & Atmosphere 12(2): 18–20.
Green, M. (2003.) The dance of the turbid fringe. Water & Atmosphere 11(2): 20–21.
Green, M.; Ellis, J.; Schwarz, A.-M.; Lind, D.; Bluck, B. (2003).

The Resource Management Act 1991 (RMA) dictates how we are to manage our physical environment, including the coast and estuaries.

A model is a representation of a “real thing”. Usually, the model is simpler in some or many ways than the real thing; the model simulates the behaviour of the real thing; and the model can be used to predict the future behaviour of the real thing.

Monitoring is often an expensive exercise, but it does not have to be.

Estuaries are more than just the mudflats that we cross on the way to the beach. Of course they have intrinsic value – what natural environment doesn’t? – but they also provide us humans with a range of ecological services that help to sustain the quality of our environment, and with amenities that we all enjoy, and sometimes profit from.

Over the past decade, NIWA has published many popular articles that deal with estuaries - this overview is intended to bring together and make whole sense of the information published to date in the various popular articles.

An estuary is a semi-enclosed embayment, with a free connection to the sea at one end and a freshwater supply at the other.

Salmon, Trout and Char (Salmonidae) The Salmonidae family is native to the Northern Hemisphere, but several species have been introduced to New Zealand. Some of these species, particularly brown and rainbow trout, have established very successfully here and support New Zealand’s reputation as an angling Eldorado.

Other live bearers (Phallocerus caudimaculatus, Poecilia latipinna, P. reticulata, Xiphophorus helleri) In addition to mosquitofish, there are four other species of Poeciliidae in New Zealand. As all of these have a very restricted distribution, they have been combined for this discussion. They are all popular aquarium species (who has not heard of the guppy) and probably came to be released by aquarists either tired of looking after their fish or eager to establish feral populations in New Zealand.

LIVE BEARERS (Poeciliidae) As the common name of this family implies, the Poeciliidae are characterised by giving birth to live young. Other family characteristics include a single soft-rayed dorsal fin and no lateral line. On male poeciliids, the anal fin has evolved into a structure known as a gonopodium that is used to transfer sperm bundles to the female fish.