The torrentfish (Cheimarrichthys fosteri) is the only species in the family Cheimarrichthyidae in the world!
It is found in fast-flowing rivers with a gravel substrate, often occupying the fastest-flowing areas particularly in riffles, rapids and torrents. It spends little time actively swimming against the rapids, living instead amongst and beneath loose gravels and cobbles. It emerges from the rapids at night to feed.
The torrentfish is well adapted to this habitat, with a flattened head and large pectoral fins to help anchor itself on the riverbed, while the raised eyes and ventral mouth are probably adaptations for feeding in this habitat.
Like many of New Zealand’s freshwater fish, the torrentfish undertakes migrations between the sea and freshwater as part of its life cycle. Although spawning sites have never been located, it is believed that male and female torrentfish migrate within freshwater habitats to spawn, with larvae moving out to sea and the juveniles returning to freshwater.
The torrentfish appears on the IUCN Red List with a conservation classification of ‘vulnerable’. This is because it requires a specialised habitat with cool, highly oxygenated, fast-flowing water, and so it is threatened by water being taken for irrigation, water pollution and climate change. River sedimentation is also a threat, as it needs to live amongst loose gravels and is less common in waterways with compacted substrate.