Galaxias


Galaxias is a genus of small freshwater fish in the family Galaxiidae, and are frequently referred to as the galaxiids. These highly adaptable fish are typically found at temperate latitudes across the Southern Hemisphere.
Galaxiids are scaleless and somewhat tubular in body form, ranging from very slender to quite bulky. They are somewhat torpedo-shaped, with the dorsal and anal fins positioned close to the tail. They are generally small, with typical adults ranging between in total length, with some stocky species attaining around. The largest, Galaxias argenteus, has been recorded at, although is a more typical adult length.

Distribution

Galaxiids are restricted to the Southern Hemisphere, and generally only occur in temperate latitudes. Only one species is known from subtropical habitats.
Galaxiids are the dominant group of native freshwater fish in New Zealand, and, along with the Percichthyidae, one of two dominant groups of native freshwater fish in southeastern Australia. Only one of the species is found in Africa, and only three are found in South America. One species is endemic to the New Caledonia

Habitat

Galaxiids are coolwater species, with many wholly freshwater species specialising in high-altitude upland streams, rivers, and lakes. Some galaxiids include a marine stage in their lifecycles where larvae are washed out to sea to develop, and return to rivers as juveniles. This type of diadromous fish migration is known as amphidromy. These species are consequently also found in low-altitude habitats, but frequently migrate to high-altitude reaches of river systems in their adult stage.

Threats

Wholly freshwater galaxiids are gravely threatened by exotic salmonid species, particularly exotic trout species, which prey heavily upon them and compete with them for food and habitat. This is a major concern, as exotic trout species have been introduced to many different land masses with no thought as to impacts on native fish such as galaxiids, and no attempt to preserve some exotic trout-free habitats for native fish.
In most situations, wholly freshwater galaxiids are unable to persist in the presence of exotic trout species, and many are now restricted to the few remaining trout-free habitats. Where these species are found in the presence of trout, the galaxiids usually consist entirely of individuals which dispersed there from an upstream trout-free population, and are not self-sustaining. Numerous localised extinctions of wholly freshwater galaxiid species have been caused by the introduction of exotic trout species and a number of wholly freshwater galaxiid species are threatened with extinction by exotic trout species and other exotic salmonids.
Introduced salmoniids also have a negative impact on diadromous galaxiids, competing with them for food and habitat, as well as preying on them. However, the impact is not as great and they appear to be able to persist in the presence of trout.

Species

The 46 recognized species in this genus are:Galaxias aequipinnis Raadik, 2014 Galaxias anomalus Stokell, 1959 Galaxias arcanus Raadik, 2014 Galaxias argenteus Gmelin, 1789 Galaxias auratus Johnston, 1883 Galaxias brevipinnis Günther, 1866 Galaxias brevissimus Raadik, 2014 Galaxias cobitinis McDowall & Waters, 2002 Galaxias depressiceps McDowall & Wallis, 1996 Galaxias divergens Stokell, 1959 Galaxias eldoni McDowall, 1997 Galaxias fasciatus Gray, 1842 Galaxias fontanus Fulton, 1978 Galaxias fuscus Mack (ornithologist)|Mack], 1936 Galaxias globiceps Eigenmann, 1928Galaxias gollumoides McDowall & Chadderton, 1999 Galaxias gracilis McDowall, 1967 Galaxias gunaikurnai Raadik, 2014 – found in the Australian Shaw Creek, Macalister River catchment, state of Victoria, AustraliaGalaxias johnstoni Scott, 1936 – found in the Tasmanian Clarence Lagoon, Derwent River catchmentGalaxias lanceolatus Raadik, 2014 Galaxias longifundus Raadik, 2014 Galaxias macronasus McDowall & Waters, 2003Galaxias maculatus Jenyns, 1842 Galaxias mcdowalli Raadik, 2014 Galaxias mungadhan Raadik, 2014 – found in the Dargo River, Mitchell River catchment, Alpine and East Gippsland, state of Victoria, AustraliaGalaxias neocaledonicus Max [Carl Wilhelm Weber|Weber] & de Beaufort, 1913 – found in New CaledoniaGalaxias niger Andrews, 1985 Galaxias occidentalis Ogilby, 1899 Galaxias olidus Günther, 1866 Galaxias oliros Raadik, 2014 Galaxias ornatus Castelnau, 1873 Galaxias parvus Frankenberg, 1968 – found in the Tasmanian Lake PedderGalaxias paucispondylus Stokell, 1938 – found in the Southern Alps of New ZealandGalaxias pedderensis Frankenberg, 1968 – found in the Tasmanian Lake PedderGalaxias platei Steindachner, 1898Galaxias postvectis F. E. Clarke, 1899 Galaxias prognathus Stokell, 1940 Galaxias pullus McDowall, 1997 Galaxias rostratus Klunzinger, 1872 Galaxias supremus Raadik, 2014 – found in the Australian Kościuszko National Park in New South Wales.Galaxias tantangara Raadik, 2014 – endemic to the Australian Tantangara Creek in the upper Murrumbidgee River system of the Kościuszko National ParkGalaxias tanycephalus Fulton, 1978 Galaxias terenasus Raadik, 2014 Galaxias truttaceus Valenciennes, 1846 Galaxias vulgaris Stokell, 1949 Galaxias zebratus Castelnau, 1861 – endemic to South Africa's Western Cape
The genus also contains several extinct species, including:†Galaxias angustiventris Schwarzhans et al., 2012 - Bannockburn Formation, New Zealand