Galaxias

For other uses, see Galaxias (disambiguation).
Galaxias
A Galaxias olidus from southeast Australia.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Actinopterygii
Order: Osmeriformes
Family: Galaxiidae
Subfamily: Galaxiinae
Genus: Galaxias
G. Cuvier, 1816

Galaxias is a genus of smallish, highly successful freshwater fishes, commonly called galaxias, in the Galaxiidae family.

Species

There are currently 46 recognized species in this genus:

Distribution

Galaxias are restricted to the Southern Hemisphere, and generally only occur in temperate latitudes. Only one species is known from subtropical habitats.[3]

Before European settlement, galaxias were 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 (G. zebratus) is found in Africa, and only three (G. globiceps, G. maculatus and G. platei) are found in South America.

Habitat

Galaxias are coolwater species, with many wholly freshwater species specialising in high-altitude upland streams (including very small streams), rivers, and lakes. Some Galaxias species include a marine stage in their lifecycles where larvae are washed out to sea to develop, and return to rivers as juveniles. These species are consequently also found in low-altitude habitats, but frequently migrate to high-altitude reaches of river systems in their adult stage.

Wholly freshwater Galaxias species are gravely threatened by exotic salmonid species, particularly exotic trout species, which prey heavily upon them and compete with them for food. This is a major concern, as exotic trout species have been recklessly introduced to many different land masses (e.g. Australia, New Zealand, South Africa), with no thought as to impacts on native fish such as galaxias, and no attempt to preserve some exotic trout-free habitats for native fish.[4]

In most situations, wholly freshwater galaxias species show a complete inability to survive in the presence of exotic trout species, and many now occur only in the rare trout-free habitats still available to them. Numerous localised extinctions of wholly freshwater galaxias species (i.e. mountain galaxias) have been caused by the introduction of exotic trout species (including ongoing illegal stockings) and a number of wholly freshwater galaxias species are threatened with overall extinction by exotic trout species and other exotic salmonids.[3]


References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 Raadik, T.A. (2014). "Fifteen from one: a revision of the Galaxias olidus Günther, 1866 complex (Teleostei, Galaxiidae) in south-eastern Australia recognises three previously described taxa and describes 12 new species.". Zootaxa, 3898 (1): 1–198.
  2. ↑ Precious: Gollum (the fish) risks extinction in New Zealand
  3. ↑ 3.0 3.1 McDowall, R.M. (2006): Crying wolf, crying foul, or crying shame: alien salmonids and a biodiversity crisis in the southern cool-temperate galaxioid fishes? Reviews in Fish Biology and Fisheries, 16: 233–422.
  4. ↑ Biodiversity, Alien trout, and the "So what" attitude

External links