Five species of Neochanna mudfish are nondiadromous derivatives of the diadromous Tasmanian mudfish. The New Zealand species are widespread from far Northland to the eastern central South Island. They are in general allopatric, though two species are found in close proximity in northern latitudes. They are all found in wetlands, often in debris-filled habitats and have distinctive specialisations that adapt them to living in such places. They are capable of aestivation when aquatic habitats dry up. Brown mudfish is present on both sides of Cook Strait, probably a direct consequence of land connections across the strait at times of lowered sea levels in the Pleistocene. Absence of brown mudfish from South Westland reflects Pleistocene glaciation there. A mudfish species on the Chatham Islands, east of mainland New Zealand, is the only non-diadromous species on the island, and its presence there must post-date the emergence of the islands from marine submergence, believed to have been late in the Cenozoic.