Galaxias
| Galaxias | |
|---|---|
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|
| 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 small, highly successful freshwater fish in the Galaxiidae family. They are typically found at temperate latitudes across the Southern Hemisphere and are frequently referred to as galaxiids.
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 adult lengths ranging between 4–15 cm (1.6–5.9 in) in total length, with some stocky species attaining around 25 cm (10 in). The largest, Galaxias argenteus, has been recorded at 58 cm (1.90 ft), although 30–40 cm (12–16 in) is a more typical adult length.
The 46 recognized species in this genus are:
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 (G. zebratus) is found in Africa, and only three (G. globiceps, G. maculatus, and G. platei) are found in South America.
Galaxiids are coolwater species, with many wholly freshwater species specialising in high-altitude upland streams (including very small 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.
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 (e.g. Australia, New Zealand, South Africa) 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.
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Wikipedia