Eldon's galaxias

Species of fish
Speciesbox
| name = Eldon's galaxias
| image = Eldon's galaxias (Galaxias eldoni) (head). jpg
| image caption =
| status = CR
| status system = IUCN3.1
| status ref =
| status2 = NE
| status2 system = NZTCS
| status2 ref = The name recognises the ichthyologist G. A. (Tony) Eldon, who helped collect specimens and had retired not long before McDowall described this species. Unlike all other Galaxias (except G. divergens), it has only 15 caudal fin rays and no pyloric caeca. It is a relatively good climber, able to wriggle up wet rocky slopes, and is able to negotiate waterfalls up to 3 m high. It tends to be found upstream of waterfalls that block the movement of introduced salmonid fishes such as brown trout, rainbow trout, and brook char. Its original distribution was likely much larger, but trout species have eradicated it in all but the headwaters which make up its current home range. Larvae hatch 4–6 weeks later. The larvae are large and are able to swim effectively; they do not disperse far from where they were spawned.

This species is rated Nationally Endangered by the Department of Conservation and critically endangered by the IUCN, due to its small number of streams it occupies (an area of just 0.69 km2) and the threats of invasive species. Because G. eldoni lays very few eggs and has large, poorly dispersing fry, it is vulnerable to predation by introduced trout. Since the species was described in 1997 several small populations have been driven extinct from conversion of land to forestry or farming. The building of irrigation canals has allowed the closely related species Galaxias pullus to invade its range and hybridise with it. Currently there are protected areas for this species in the Lammerlaw Range, but they are vulnerable to being invaded by trout, or trout being deliberately introduced.