Mudfish/hauhau/waikaka/kōwaro are small, native freshwater fish regarded as a taonga (treasured) species to iwi.
They are eel-like in appearance, with long, stocky bodies, thick slippery skin, and no scales. Mudfish are found in swampy lowland habitats such as wetlands, pākihi, pools in swamp forests and slow-flowing streams and drains. However the Chatham Island mudfish are an exception, as they live around the margins of peat lakes.
Mudfish vary in size between species, but adults grow to around 9–12 cm long. Some of the largest mudfish found have been up to 17.5 cm in length.
There are five species of mudfish in New Zealand, all of which are either 'At Risk' or 'Threatened' under the NZ Threat Classification System.
Northland/burgundy mudfish are found only in Northland, around Kerikeri and Ngawha— populations are confined to a small area within a 25 km radius of Lake Omapere.
Black mudfish are found in a variety of wetland types from Waikato to the far north.
Brown mudfish are the most widespread mudfish species in New Zealand, found in Taranaki, the lower North Island, and the West Coast of the South Island.
Chatham Island mudfish are the most recently discovered NZ mudfish species. So far, they are only known from three lakes and a stream on Chatham Island.
Canterbury mudfish are the most threatened of New Zealand's mudfish species. They are found in a limited number of waterways in the Canterbury Plains, between the Ashley River (in the north) and the Waitaki River (in the South).
More information about this species can be found on the Canterbury mudfish website.
Canterbury mudfish: the most threatened of New Zealand's mudfish species
Mudfish were once widespread throughout lowland wetland habitats, but are now found at a relatively small number of sites, many of which are on private land. The Department of Conservation is working with landowners to protect these key remaining habitats.
A very special fish
Mudfish have the ability to survive during times when there is no surface water—something most other fish can't do!
Brown mudfish: the most widespread mudfish species in New Zealand
During these 'dry' periods, their metabolism slowly drops and they absorb oxygen through their skin. Mudfish can usually only cope with short periods of time without water, but have sometimes been known to survive for several months after surface water dries.
However, surviving during 'dry' periods is very hard on mudfish, and after water returns mudfish are often thin, in poor condition, and can have lower breeding success.
Mudfish need to have damp surroundings and cover, such as logs, tree roots and vegetation, to keep them alive during these times. When surface water returns, they become active again immediately—ready to swim, eat and breed.
Their ability to survive in these conditions means that mudfish can live in places other fish can't.