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Galaxiidae

The Galaxiidae are a family of mostly small freshwater fish in the Southern Hemisphere. The majority live in Southern Australia or New Zealand, but some are found in South Africa, southern South America, Lord Howe Island, New Caledonia, and the Falkland Islands. One galaxiid species, the common galaxias (Galaxias maculatus), is probably the most widely naturally distributed freshwater fish in the Southern Hemisphere. They are coolwater species, found in temperate latitudes, with only one species known from subtropical habitats.[1] Many specialise in living in cold, high-altitude upland rivers, streams, and lakes.

Galaxiidae
Temporal range: Early Miocene to present Possible Maastrichtian occurrence
A mountain galaxias (Galaxias olidus)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Cohort: Euteleostei
Order: Galaxiiformes
Family: Galaxiidae
Bonaparte 1832
Genera

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Some galaxiids live in fresh water all their lives, but many have a partially marine lifecycle. In these cases, larvae are hatched in a river, but are washed downstream to the ocean, later returning to rivers as juveniles to complete their development to full adulthood. This pattern differs from that of salmon, which only return to fresh water to breed, and is described as amphidromous.[2]

Freshwater galaxiid species are gravely threatened by exotic salmonid species, particularly trout species, which prey upon galaxiids and compete with them for food. Exotic salmonids have been recklessly introduced to many different land masses (e.g. Australia, New Zealand), with no thought as to impacts on native fish, or attempts to preserve salmonid-free habitats for them. Numerous localised extinctions of galaxiid species have been caused by the introduction of exotic salmonids, and a number of freshwater galaxiid species are threatened with overall extinction by exotic salmonids.[1]

Evolution

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Phylogenetic evidence alternatively places galaxiids within the Protacanthopterygii, or more recently as the sister group to the Neoteleostei. Their ancestors are thought to have diverged from the neoteleosts around the Triassic-Jurassic boundary.[3][4]

The earliest definitive fossils of galaxiids are from the Miocene of New Zealand, which can be placed in the extant genus Galaxias. This young fossil range contrasts with the presumed ancient origins of the group. In 1998, a possible Late Cretaceous (Maastrichtian) galaxiid from South Africa was described as Stompooria.[5] However, later studies have questioned this assignment, as Stompooria differs from galaxiids in many morphological traits, especially in the presence of scales, although it being an ancestral galaxiid that had not yet developed galaxiid traits could not be ruled out.[6] Other taxonomic treatments have instead placed Stompooria as part of an extinct clade sister to the Esociformes and Salmoniformes.[4]

Taxonomic diversity

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About 50 species are in the family Galaxiidae, grouped into seven genera:[7]

Genera

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  • ?†Stompooria Anderson, 1998 (Maastrichtian of South Africa; assignment disputed, possibly a stem-salmoniform)[5][6]
  • Subfamily Aplochitoninae Begle 1991
    • Genus Aplochiton Jenyns 1842 [Haplochiton Agassiz 1846; Farionella Valenciennes 1850 ex Cuvier & Valenciennes 1850] (two species)
    • Genus Lovettia McCulloch 1915 (one species)
  • Subfamily Galaxiinae [Paragalaxiinae Scott 1936]
    • Genus Brachygalaxias Eigenmann 1928 (two species)
    • Genus Galaxias Cuvier 1816 [Saxilaga Scott 1936; Galaxias (Agalaxis) Scott 1936; Agalaxis (Scott 1936); Lyragalaxias Whitley 1935; Austrocobitis Ogilby 1899; Mesites Jenyns 1842 non Schoenherr 1838 non Geoffroy 1838; Nesogalaxias Whitley 1935] (34 species)
    • Genus Galaxiella McDowall 1978 (four species)
    • Genus Neochanna Günther 1867 [Saxilaga (Lixagasa) Scott 1936; Lixagasa (Scott 1936); Saxilaga Scott 1936] (six species)
    • Genus Paragalaxias Scott 1935 [Querigalaxias Whitley 1935] (four species)

Species by geography

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Australia

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Galaxiids are found around the south eastern seaboard of Australia and in some parts of south western Australia. The galaxiids and the temperate perches (Percichthyidae) are the dominant native freshwater fish families of southern Australia. Species common to all areas include:

South east Australian mainland

Threatened species are:

Western Australia

Tasmania Seventeen species of galaxiids have been found in Tasmania. The most common species are:

Tasmanian endangered species include:

New Zealand

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Twenty-three species of galaxiids have been discovered in New Zealand, and prior to the introduction of non-native species such as trout, they were the dominant freshwater fish family. Most of these live in fresh water all their lives. However, the larvae of five species of the genus Galaxias develop in the ocean, where they form part of the zooplankton and return to rivers and streams as juveniles (whitebait), where they develop and remain as adults. All Galaxias species found in New Zealand are endemic, except for Galaxias brevipinnis (koaro) and Galaxias maculatus (inanga).

South America

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South Africa

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Fishing

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The juveniles of those galaxiids that develop in the ocean and then move into rivers for their adult lives are caught as whitebait while moving upstream and are much valued as a delicacy. Adult galaxiids may be caught for food, but they are generally not large. In some cases, their exploitation may be banned (e.g. New Zealand) unless available to indigenous tribes.

In addition to serious impacts from exotic trout species, Australian adult galaxiids suffer a disregard from anglers for being "too small" and "not being trout". This is despite the fact that several Australian galaxiid species, though smallish, grow to a sufficient size to be catchable and readily take wet and dry flies, and that one of these species — the spotted galaxias — was keenly fished for in Australia before the introduction of exotic trout species. A handful of fly-fishing exponents in Australia are rediscovering the pleasure of catching (and releasing) these Australian native fish on ultralight fly-fishing tackle.

References

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  1. ^ a b 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 (3–4): 233–422. Bibcode:2006RFBF...16..233M. doi:10.1007/s11160-006-9017-7. S2CID 11504101.
  2. ^ McDowall, Robert M. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 117. ISBN 978-0-12-547665-2.
  3. ^ Near, Thomas J.; et al. (2012). "Resolution of ray-finned fish phylogeny and timing of diversification". PNAS. 109 (34): 13698–13703. Bibcode:2012PNAS..10913698N. doi:10.1073/pnas.1206625109. PMC 3427055. PMID 22869754.
  4. ^ a b Near, Thomas J.; Thacker, Christine E. (2024). "Phylogenetic Classification of Living and Fossil Ray-Finned Fishes (Actinopterygii)". Bulletin of the Peabody Museum of Natural History. 65 (1): 3–302. doi:10.3374/014.065.0101. ISSN 0079-032X.
  5. ^ a b Anderson, M. Eric. "A late Cretaceous (Maasteichtian) Galaxiid fish from South Africa". Special Publication (60): 1–8. ISSN 0075-2088.
  6. ^ a b McDowall, Robert M.; Burridge, Christopher P. (2011). "Osteology and relationships of the southern freshwater lower euteleostean fishes". Zoosystematics and Evolution. 87 (1): 7–185. doi:10.1002/zoos.201000020.
  7. ^ Froese, Rainer; Pauly, Daniel (eds.). "Family Galaxiidae". FishBase. July 2021 version.
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