Eldon's galaxias (Galaxias eldoni) is an endangered galaxiid fish endemic to New Zealand. One of several fishes in the genus Galaxias found in Central Otago, it has a very small home range and is at risk of being driven to extinction by trout introduced for recreational fishing. Taxonomy Eldon's galaxias was described in 1997 by New Zealand freshwater ichthyologist Bob McDowall from specimens collected in 1995 and 1996. It is part of the Galaxias vulgaris species complex, and differs from Galaxias pullus, another new species McDowall had found in the same area genetically and by its colour pattern: irregular stripes that continue across its back. The name recognises the ichthyologist G. A. (Tony) Eldon, who helped collect specimens and had retired not long before McDowall described this species. Description Galaxias eldoni is an elongated, deep-bodied Galaxias, usually 80 mm in length (although very large individuals can reach 155 mm). Its snout shape is variable depending on whether it lives on a stream or wetland habitat. It has large pectoral and pelvic fins, and a dorsal fin that starts forward of the anal fin. It is orange-brown to olive-brown with very variable dark brown markings that can be speckles, spots, or irregular bands, and its skin is heavily dusted with gold. Sometimes it has a small black patch behind the gill cover (operculum). Unlike all other Galaxias (except G. divergens), it has only 15 caudal fin rays and no pyloric caeca. Habitat and distribution This species lives only in eastern waterways of Otago, in wetlands and small streams that flow into the Taieri, Tokomairiro and Waipori rivers and below Lake Mahinerangi. These streams tend to be shallow, fast flowing and stony, ranging from lowland forested areas to alpine. G. eldoni lives among the gravels or under the banks of the waterway. 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. Feeding Galaxias eldoni feeds on small freshwater invertebrates such as stoneflies and mayflies. They will also feed on larger prey like freshwater crayfish/kōura, and food that