New Zealand’s largest group of freshwater fish are galaxiids from the Galaxiidae family. The 30 species include īnanga, kōkopu, kōaro and mudfish.
The name ‘galaxiid’ refers to the clusters or ‘galaxies’ of golden or silvery star-like patterns on their scaleless bodies – perfect camouflage in the dappled light of the small forest streams they tend to favour. They are also found in swamps, drains and larger waterways. Most of the galaxiids are great climbers, able to scale waterfalls helped by ridges on their fins.
Galaxiids have sensors on their head and body – the lateral line – this is part of the non-visual sensory systems of all fish. However, kōkopu species have evolved to use the sensors on the head to detect when and where something hits the water, enabling them to feed on insects that fall from overhanging plants at night.
The galaxiid diet is predominantly invertebrates – both aquatic species, including a number of macroinvertebrates, and those that fall into the water.
Many of our native galaxiids are threatened, with nearly half of them appearing on the IUCN Red List. The tiny lowland longjaw galaxias (Galaxias cobitinis) is New Zealand’s rarest native fish and is listed as ‘critically endangered’.
Acknowledgement: Upland longjaw galaxias (Galaxias prognathus), Simon Elkington, Department of Conservation. Creative Commons 4.0