Mudfish are probably one of the least known freshwater fish. There are five species in New Zealand, and they have become specialised for life in a distinctive type of habitat – swamps, drains, and forest pools that tend to dry up in summer. They can exist in these habitats because they have the ability to survive out of water during drought. In fact, the first records of these fish often came because specimens were discovered curled up in the mud when wet areas were dug up for drainage or cultivation.
Mudfish are an elongate, slender-bodied fish with blunt heads and small eyes. Three of the five species lack pelvic fins, and this is the easiest way to distinguish them from other members of the Galaxiidae family.
The brown mudfish occupies central New Zealand, from Taranaki, through Wellington and the Wairarapa, and down the northwest coast of the South Island. As its distribution does not overlap with the other mudfish species, there is little chance of confusing this species with the others.
Studies show that mudfish mature during the summer aestivation period and spawn as soon as their habitat is re-inundated in the autumn. This gives the larvae the longest possible period with water present in which to develop and grow. Not all brown mudfish aestivate as some live in permanent water. These populations may spawn at any time of the year. Brown mudfish reach a maximum age of at least seven years and grow to about 150 mm in length.