The alpine river galaxias, Galaxias paucispondylus, is a galaxiid

Galaxiid

The Galaxiidae, also known by the anglicised name as galaxiids, are a family of mostly small freshwater fish in the southern hemisphere. The majority of species live in Australia or New Zealand, some are also found in South Africa, South America, Lord Howe Island, New Caledonia and the Falkland...

 of the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Galaxias

Galaxias

Galaxias is the common name for a large group of smallish, highly successful freshwater fish in the Galaxias genus and Galaxiidae family. Galaxias are restricted to the southern hemisphere, and generally only occur in temperate latitudes; only one species is known from sub-tropical habitat...

, found only in mid to high altitude streams flowing from the Southern Alps

Southern Alps

The Southern Alps is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the island's western side...

 of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

. It grows to a length of up to 11 cm.

Alpine galaxias are speckled olive-green over a light brown base. The single large dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 is rounded, and set back two thirds of the body length, the anal fin a little further back. The caudal fin is large and slightly forked. Like all galaxiids it lacks scale

Scale (zoology)

In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s and has a thick, leathery skin covered with mucus

Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

.

They are non-diadromous and therefore do not have a marine phase and are not part of the whitebait

Whitebait

Whitebait is a collective term for the immature fry of fish, typically between 25 and 50 millimetres long. Such young fish often travel together in schools along the coast, and move into estuaries and sometimes up rivers where they can be easily caught with fine meshed fishing nets...

catch.