Eldon's galaxias

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Eldon's galaxias
Eldon's galaxias (Galaxias eldoni) (head).jpg
Status NZTCS NE.svg
Nationally Endangered (NZ TCS) [1]
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Galaxiiformes
Family: Galaxiidae
Genus: Galaxias
Species:
G. eldoni
Binomial name
Galaxias eldoni
McDowall, 1997
Eldon's galaxias distribution map.png
Range of Galaxias eldoni

Eldon's galaxias (Galaxias eldoni) is an endangered galaxiid fish endemic to New Zealand. One of several fishes in the genus Galaxias found in Central Otago, it has a very small home range and is at risk of being driven to extinction by trout introduced for recreational fishing.

Contents

Taxonomy

Eldon's galaxias was described in 1997 by New Zealand freshwater ichthyologist Bob McDowall from specimens collected in 1995 and 1996. It is part of the Galaxias vulgaris species complex, and differs from Galaxias pullus , another new species McDowall had found in the same area genetically and by its colour pattern: irregular stripes that continue across its back. [2] The name recognises the ichthyologist G. A. (Tony) Eldon, who helped collect specimens and had retired not long before McDowall described this species. [3]

Description

Galaxias eldoni from a stream in the Lammerlaw Ranges, Otago, New Zealand Eldon's galaxias (Galaxias eldoni).jpg
Galaxias eldoni from a stream in the Lammerlaw Ranges, Otago, New Zealand
G. eldoni has irregular brown markings and a dusting of gold. Eldon's galaxias (Galaxias eldoni) - closeup of skin.jpg
G. eldoni has irregular brown markings and a dusting of gold.
External video
Nuvola apps kaboodle.svg Wild Dunedin: Eldon's Galaxias – last chance to see (2010 short film by Roland Kahurangi)

Galaxias eldoni is an elongated, deep-bodied Galaxias, usually 80 mm in length (although very large individuals can reach 155 mm). [3] Its snout shape is variable depending on whether it lives on a stream or wetland habitat. It has large pectoral and pelvic fins, and a dorsal fin that starts forward of the anal fin. It is orange-brown to olive-brown with very variable dark brown markings that can be speckles, spots, or irregular bands, and its skin is heavily dusted with gold. Sometimes it has a small black patch behind the gill cover (operculum). [3] Unlike all other Galaxias (except G. divergens), it has only 15 caudal fin rays and no pyloric caeca. [2]

Habitat and distribution

Habitat of Eldon's galaxias: a deep spring-fed stream on the Lammerlaw Range. Eldon's galaxias (Galaxias eldoni) habitat.jpg
Habitat of Eldon's galaxias: a deep spring-fed stream on the Lammerlaw Range.

This species lives only in eastern waterways of Otago, in wetlands and small streams that flow into the Taieri, Tokomairiro and Waipori rivers and below Lake Mahinerangi. These streams tend to be shallow, fast flowing and stony, ranging from lowland forested areas to alpine. G. eldoni lives among the gravels or under the banks of the waterway. [1] It is a relatively good climber, able to wriggle up wet rocky slopes, and is able to negotiate waterfalls up to 3 m high. [4] It tends to be found upstream of waterfalls that block the movement of introduced salmonid fishes such as brown trout, rainbow trout, and brook char. [5] Its original distribution was likely much larger, but trout species have eradicated it in all but the headwaters which make up its current home range. [2]

Feeding

Galaxias eldoni feeds on small freshwater invertebrates such as stoneflies and mayflies. They will also feed on larger prey like freshwater crayfish/kōura, and food that is carried by the current. [5]

Life cycle

Unlike the more well-known 'whitebait' Galaxias species, G. eldoni is not diadromous; its entire life is spent in fresh water. It is long-lived, 15 years or longer; some fully-grown individuals have been tagged and then recaptured 10 years later. [3] It is slow growing, reaching maturity at one (males) or two years (females). Females produce low numbers of large eggs during October. Spawning occurs at the stream edge in riffles, and eggs are laid directly into the stony stream bottom. [6] Larvae hatch 4–6 weeks later. The larvae are large and are able to swim effectively; they do not disperse far from where they were spawned. [7]

Conservation

Electrofishing for Eldon's galaxias (Galaxias eldoni) in a deep spring-fed stream on the Lammerlaw ranges, Otago, New Zealand. Eldon's galaxias (Galaxias eldoni) electrofishing.jpg
Electrofishing for Eldon's galaxias (Galaxias eldoni) in a deep spring-fed stream on the Lammerlaw ranges, Otago, New Zealand.

This species is rated Nationally Endangered by the Department of Conservation and critically endangered by the IUCN, due to its small number of streams it occupies (an area of just 0.69 km2) and the threats of invasive species. Because G. eldoni lays very few eggs and has large, poorly dispersing fry, it is vulnerable to predation by introduced trout. Since the species was described in 1997 several small populations have been driven extinct from conversion of land to forestry or farming. [7] The building of irrigation canals has allowed the closely related species Galaxias pullus to invade its range and hybridise with it. [7] Currently there are protected areas for this species in the Lammerlaw Range, but they are vulnerable to being invaded by trout, or trout being deliberately introduced. [3]

Related Research Articles

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, 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. Many specialise in living in cold, high-altitude upland rivers, streams, and lakes.

Climbing galaxias

The climbing galaxias or kōaro is a fish of the family Galaxiidae found in Australia, New Zealand, and nearby islands. The name climbing galaxias is used in Australia, and koaro or kōaro in New Zealand. Further vernacular names include short-finned galaxias, broad-finned galaxias, Cox's mountain galaxias, and Pieman galaxias.

The common galaxias or inanga is a very widespread Southern Hemisphere fish in the family Galaxiidae. It is slim, narrow fish with a forked tail and a mottled, spotty pattern, typically about 10 cm (4 in) long when fully grown. It lives in fresh water, but spawns at river mouths and spends the first six months of its life at sea, returning en masse in spring. Its vernacular names include cowfish, jollytail, common jollytail, eel gudgeon, inaka, native trout, pulangi, puye, slippery tarki, spotted minnow and whitebait.

Galaxias olidus

Galaxias olidus, the mountain galaxias, is a species of freshwater galaxiid fish widely found in southeastern Australia.

Galaxias fuscus, the barred galaxias, is a galaxiid of the genus Galaxias, a member of the Mountain Galaxias species complex group of freshwater fish, found in Australia.

The Chatham mudfish, formerly known as the Chathams galaxias, is a galaxiid fish endemic to two small, peaty lakes in southern Chatham Island, New Zealand.

Tasmanian mudfish

The Tasmanian mudfish, Neochanna cleaveri, is a small Australian amphidromous fish in the galaxiid family, of the order Osmeriformes.

Banded kokopu

The banded kokopu is a galaxiid of the genus Galaxias, found only in New Zealand, including the Chatham and Stewart/Rakiura islands. It commonly grows to 20–25 cm, but has been recorded growing to around 30 cm. Juvenile banded kokopu are good climbers and can climb up waterfalls and other vertical surfaces by moving into the splash zone and wriggling up the surface, using the water surface tension and their large downturned fins for grip.

Shortjaw kokopu

The shortjaw kokopu is a galaxiid fish, endemic to New Zealand. They are large, scaleless fish which inhabit stable pools in cascading, bouldery streams with forest cover. Shortjaw kokopu are amphidromous, with the fry going to sea after hatching, and returning as juveniles to fresh water where they grow to adulthood. They may grow to a maximum of 350 mm (14 in) in total length, but more commonly reach 150–200 mm (5.9–7.9 in).

Giant kōkopu

The giant kōkopu is a threatened species of ray-finned fish in the genus Galaxias, found only in New Zealand. It can reach up to 58 cm (23 in) in length and 2.7 kg (6.0 lb) in weight, making it the largest species in the family Galaxiidae. It is a mainly lowland species, commonly found in slow-flowing streams, wetlands, lakes, and lagoons. Most populations have an amphidromous life cycle, with larvae going to sea soon after hatching and returning about four months later as small juveniles, 4.5–5 cm (1.8–2.0 in). Juvenile giant kōkopu form a small part of the annual whitebait catch.

Dwarf inanga

The dwarf inanga is a galaxiid of the genus Galaxias, found in the North Island of New Zealand.

The lowland longjaw galaxias is a galaxiid of the genus Galaxias, found only in the South Island of New Zealand, in the Kauru River, a tributary of the Kakanui River in north Otago, and in parts of the upper Waitaki catchment. It grows to a length of up to 7 cm.

Common river galaxias

The common river galaxias or Canterbury galaxias is a galaxiid fish of the genus Galaxias, found only in Canterbury, New Zealand.

Redfin bully

The redfin bully is a species of freshwater fish in the family Eleotridae endemic to New Zealand. Being amphidromous, it spends part of its life cycle at sea. Males have distinctive bright red patterns and stripes on their fins. Adults grow to an average of 80–100 mm (3.1–3.9 in) total length, with a maximum of 120 mm (4.7 in).

<i>Galaxias</i>

Galaxias is a genus of small, highly successful freshwater fish in the family Galaxiidae. They are typically found at temperate latitudes across the Southern Hemisphere and are frequently referred to as galaxiids.

Whitebait

Whitebait is a collective term for the immature fry of fish, typically between 1 and 2 inches long. Such young fish often travel together in schools along the coast, and move into estuaries and sometimes up rivers where they can be easily caught with fine meshed fishing nets. Whitebaiting is the activity of catching whitebait.

Robert (Bob) Montgomery McDowall was one of New Zealand's most prominent freshwater ichthyologists.

Galaxias mcdowalli, McDowall's galaxias, is a galaxiid of the genus Galaxias, a member of the Mountain Galaxias species complex group of freshwater fish, found in Australia.

Galaxias supremus, the Kosciuszko galaxias, is a galaxiid of the genus Galaxias, a member of the Mountain Galaxias species complex group of freshwater fish, found in Australia.

Galaxias terenasus, the roundsnout galaxias, is a galaxiid of the genus Galaxias, a member of the Mountain Galaxias species complex group of freshwater fish, found in Australia.

References

  1. 1 2 "Eldon's galaxias". Department of Conservation. Retrieved 3 August 2017.
  2. 1 2 3 McDowall, R. M. (1997). "Two further new species of Galaxias (Teleostei: Galaxiidae) from the Taieri river, southern New Zealand [pullus, eldoni]". Journal of the Royal Society of New Zealand. 27 (2): 199–217. doi:10.1080/03014223.1997.9517533. ISSN   0303-6758.
  3. 1 2 3 4 5 McQueen, S.; Morris, R. (2013). A Photographic Guide To Freshwater Fishes of New Zealand. Auckland: New Holland. ISBN   978 1 86966 386 5.
  4. Allibone, R. M.; Townsend, C. R. (1997). "Distribution of four recently discovered Galaxiid species in the Taieri River, New Zealand: the role of macrohabitat". Journal of Fish Biology. 51 (6): 1235–1246. doi:10.1006/jfbi.1997.0524. ISSN   0022-1112.
  5. 1 2 "Eldon's galaxias". NIWA. Retrieved 3 August 2017.
  6. Allibone, R. M.; Townsend, C. R. (1997). "Reproductive biology, species status and taxonomic relationships of four recently discovered Galaxiid fishes in a New Zealand river". Journal of Fish Biology. 51 (6): 1247–1261. doi:10.1006/jfbi.1997.0523. ISSN   0022-1112.
  7. 1 2 3 Allibone, R.; Closs, G.; Hitchmough, R.; Ling, N.; David, B.; West, D.; Franklin, P.; Crow, S. (2014). "Galaxias eldoni". IUCN Red List of Threatened Species . 2014. Retrieved 3 August 2017.