The Canterbury galaxias is a non-diadromous galaxiid that inhabits low to high altitude rivers and streams in the Canterbury Plains. Previously, the Canterbury galaxias and the Otago/Southland galaxiids were thought to be the same species, but DNA analysis revealed that the Canterbury galaxias is different to the others. The Otago/Southland group has now split into eight species, although three of these await formal recognition. Detailed study of the Canterbury galaxias shows that more than one species occurs in this region as well. The new and as yet undescribed species is thought to occur in the northern part of the range – from the Clarence River north.
There are three galaxiid species that co-exist with the Canterbury galaxias and that might be confused with this species. Alpine and longjaw galaxias are relatively easy to distinguish, but the koaro is more difficult. Both the alpine and longjaw galaxias are very slender fish, and when alive, the alpine galaxias has distinct white chevron-shaped marks at the front of the dorsal fin. The long, protruding jaw of the longjaw galaxias is unmistakable. In koaro, the lower jaw is obviously shorter than the upper jaw, and this feature can be used to tell it apart from the Canterbury galaxias. Koaro also have a bolder colour pattern with sparkling gold highlights whereas the colouration of the Canterbury galaxias tends to be more subdued. However, colour can vary so much in individual fish that this is not an infallible characteristic to use for identification.
Studies show that Canterbury galaxias spawn in September and that mortality of adults can be high after spawning. The male fish excavates a primitive nest, usually under a boulder, and probably mates with several females. Although he guards the nest for a period while attracting females to breed, there is no evidence of any parental care of the eggs or larvae.