Galaxiidae

The Galaxiidae are a family of small freshwater fish found across the Southern Hemisphere. Most species live in southern Australia and New Zealand, though others inhabit South Africa, southern South America, Lord Howe Island, New Caledonia, and the Falkland Islands. The common galaxias (Galaxias maculatus) is likely the most widely naturally distributed freshwater fish in the Southern Hemisphere. These fish prefer cool waters in temperate regions; only one species lives in subtropical habitats. Many are adapted to cold, high-altitude rivers, streams, and lakes. Some galaxiids spend their entire lives in freshwater, but many have a partially marine life cycle. In these species, larvae hatch in rivers, wash downstream to the ocean, and later return to rivers as juveniles to mature. This pattern, called amphidromy, differs from salmon, which only return to freshwater to breed. Freshwater galaxiids face serious threats from introduced salmonid species, especially trout. These exotic fish prey on galaxiids and compete for food. Humans have introduced salmonids to many regions, such as Australia and New Zealand, often without considering the ecological impact on native fish. This has caused numerous local extinctions of galaxiids, and several freshwater species now face overall extinction due to salmonids. **Evolution** Phylogenetic evidence places galaxiids either within the Protacanthopterygii or, more recently, as the sister group to the Neoteleostei. Their ancestors likely diverged from neoteleosts around the Triassic-Jurassic boundary. The oldest definite galaxiid fossils come from the Miocene of New Zealand and belong to the modern genus *Galaxias*. This young fossil record contrasts with the group’s presumed ancient origins. In 1998, a possible Late Cretaceous (Maastrichtian) galaxiid from South Africa was named *Stompooria*, but later studies questioned this classification because *Stompooria* differs in many traits, especially in having scales. It might be an ancestral galaxiid that hadn’t yet developed typical galaxiid features, or it may belong to an extinct clade related to Esociformes and Salmoniformes. Many galaxiid genera show an unusual pattern where a genus from Australasia is more closely related to a genus from South America than to other genera on the same continent. For example, the South American *Aplochiton* is closely related to the Australian *Lovettia*. This pattern suggests that galaxiid evolution was influenced by the Antarctic land bridge, which once connected Australia and South America, allowing dispersal via shallow marine and freshwater routes. **Taxonomic diversity** About 50 species belong to the family Galaxiidae, divided into seven genera:

- ?†*Stompooria* (Maastrichtian of South Africa; assignment disputed) - Subfamily Aplochitoninae: *Aplochiton* (two species), *Lovettia* (one species) - Subfamily Galaxiinae: *Brachygalaxias* (two species), *Galaxias* (34 species), *Galaxiella* (four species), *Neochanna* (six species), *Paragalaxias* (four species)

**Species by geography**

*Australia* Galaxiids live along the southeastern seaboard and parts of southwestern Australia. Along with temperate perches (Percichthyidae), they are the dominant native freshwater fish in southern Australia. Common species include the common galaxias (*Galaxias maculatus*) and spotted galaxias (*Galaxias truttaceus*). In southeastern mainland Australia, species include the climbing galaxias (*Galaxias brevipinnis*), mountain galaxias (*Galaxias olidus*), and flathead galaxias (*Galaxias rostratus*). Threatened species there include the barred galaxias (*Galaxias fuscus*), dwarf galaxias (*Galaxiella pusilla*), and Tasmanian mudfish (*Neochanna cleaveri*). In Western Australia, species include the western galaxias (*Galaxias occidentalis*), mud minnow (*Galaxiella munda*), and black-stripe minnow (*Galaxiella nigrostriata*). *Tasmania* Seventeen galaxiid species have been found in Tasmania. The most common are the climbing galaxias, common galaxias, and spotted galaxias. Endangered Tasmanian species include the saddled galaxias (*Galaxias tanycephalus*), Pedder galaxias (*Galaxias pedderensis*), Swan galaxias (*Galaxias fontanus*), swamp galaxias (*Galaxias parvus*), golden galaxias (*Galaxias auratus*), dwarf galaxias, Clarence galaxias (*Galaxias johnstoni*), Tasmanian mudfish, and four species of paragalaxias: western (*Paragalaxias julianus*), Great Lake (*Paragalaxias eleotroides*), Arthurs (*Paragalaxias mesotes*), and Shannon (*Paragalaxias dissimilis*). *New Zealand* Twenty-three galaxiid species have been discovered in New Zealand.