This recently described member of the Galaxiidae family was only recognized as a distinct species in the last few years. Because this fish was first found in a swamp and has relatively large eyes, its name refers to its similarity to Gollum, a character in J.R.R. Tolkein's “The Hobbit” and “Lord of the Rings”. Recent studies at Otago University indicated that it occurs on Stewart Island, throughout the Catlins and Southland, and in the Nevis River (which used to drain into the Mataura).
The best way to tell this species apart from other galaxiids is by counting the pelvic fin rays; the Gollum galaxias has 6 pelvic fin rays whereas most of the other galaxiids usually have 7. The two galaxiids that also have 6 pelvic fin rays, Eldons and dwarf galaxias, do not co-exist with the Gollum galaxias.
No detailed studies of its life history have taken place yet, but its life cycle is probably similar to that of the other non-migratory galaxiids, with spawning taking place in spring, and the whole life cycle occurring in fresh water. The largest Stewart Island fish recorded is 75 mm, but Southland populations contain fish up to 150 mm long.