| Neochanna | |
|---|---|
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| Brown mudfish, Neochanna apoda | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Galaxiiformes |
| Family: | Galaxiidae |
| Subfamily: | Galaxiinae |
| Genus: | Neochanna Günther, 1867 |
| Species | |
See text | |
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Neochanna is a genus of galaxiid fishes, commonly known as mudfish, which are native to New Zealand and south-eastern Australia.
The recognized species in this genus are: [1]
Mudfishes are small, growing to a maximum of 180 mm (7.1 in). [2] : 303 They have a tubular, highly flexible, scaleless body with rounded fins, well-developed flanges on the caudal peduncle, tubular nostrils, small or absent pelvic fins, and mottled brown colouration. [3] Adults are active at night and are usually found in the benthic zone, while juveniles are active during the day and are found in open water. [3]
Mudfishes are found in wetlands, swamps, drains and springs. They typically live in still or slowly flowing, shallow water, with thick aquatic vegetation and overhead cover. [3]
Mudfish have the ability to aestivate during droughts, seeking out moist areas under logs and vegetation so they do not dry out. While emersed (out of the water), they respire through cutaneous respiration, either through their skin, or by taking mouthfuls of air. [2] : 304 Emersed mudfish frequently lie on their backs, possibly improving cutaneous respiration through the thinner abdominal skin, improving oxygenation of vital organs, or rehydrating skin on their upper surfaces. [3]
As wetland habitats dry out, the standing water may become stagnant and hypoxic. During this time mudfish will hang quietly at the surface with bubbles of air in their mouths to improve oxygen absorption. [3] Some choose to leave hypoxic water before it dries out, and leave again if pushed back in. [3]
While emersed they are aware of their surroundings and are responsive to change in their environment: changing position, moving to damper areas, and congregating. [3] Although they may be found deep below the surface in cavities and root holes, they do not appear to create burrows for the purpose of aestivation, with the exception of N. cleaveri . [3] Under experimental drought conditions, N. cleaveri created vertical shafts in the mud substrate, which allowed the fish to remain submersed as the free water evaporated. [4] As the water within the shaft evaporated, the mudfish excavated horizontal tunnels where they awaited the return of the water. [4] They do not feed while emersed, but may return to water at night to feed. [3]
Mudfish species are geographically widely separate, due to a combination of oceanic dispersal, sea-level change, volcanism and glaciation.
Based on anatomical and genetic data, the Tasmanian mudfish is sister to the New Zealand mudfishes. [2] : 305 The divergence is too recent for this wide distribution to result from the separation of New Zealand and Australia 83 million years ago. [2] : 305 The Tasmanian mudfish is amphidromous, spending its first 2–3 months at sea, and it is likely that this was the means of dispersal to New Zealand. All five of the New Zealand mudfishes have lost this migratory life cycle. [2] : 305
Of the New Zealand species, the Canterbury and Chatham mudfishes are the least departed from the ancestral form, retaining small pelvic fins and a more Galaxias-like shape. [5] The Chatham Islands emerged from the sea recently, possibly 2–3 million years ago, so the ancestors of the Chatham mudfish must have retained the amphidromous life cycle until after dispersal to these islands. [2] : 305 [5]
The Tasmanian mudfish is found in Tasmania and in southern Victoria, on either side of the Bass Strait, [4] and New Zealand's brown mudfish is found on either side of Cook Strait. [2] : 305 Both species likely extended their range during the Pleistocene, when the sea levels were low and there were land connections between the respective islands, and were subsequently separated when sea levels rose again. [2] : 305 [4]
There is a large gap in the brown mudfish distribution in the lower North Island. This is possibly due to the effects of volcanism causing local extinction, and the species was unable to recolonise affected catchments as it has lost the highly mobile amphidromous life cycle. [2] : 308 The absence of brown mudfish (or other Neochanna species) from the southern half of the west coast of the South Island is likely due to glaciation in the late Pleistocene, although there has been some range expansion into the glacier-affected areas. [2] : 309 [3]
The black and Northland mudfishes are the only species with a near-overlapping distribution. [2] : 308 The black mudfish is found broadly throughout the northern North Island, surrounding the much smaller distribution of the Northland mudfish, which is only found on the Kerikeri volcanic plateau. [3] It is suggested that the common ancestor of both species was found throughout the northern North Island, but it was divided into two populations by high sea levels during the Pliocene. [2] : 307 [3] These two populations then separated into the Northland mudfish in the north, and the black mudfish in the south. [6] After sea levels fell again, the black mudfish expanded its range northwards, eventually surrounding that of the Northland mudfish. [3] [6]
The Canterbury mudfish is found across the Canterbury Plains, an alluvial plain formed by large and highly mobile braided rivers. [2] : 311 The lack of genetic variation or structuring between populations suggests that these mudfish have been reduced to small founder populations, possibly due to droughts. [2] : 311 The subsequent range expansion may have been assisted by mobile braided rivers.
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.
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 a 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, Falklands minnow and whitebait.
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.
The Northland mudfish is a galaxiid of the genus Neochanna, found only in swampy locations west of the Bay of Islands in Northland, New Zealand. Its length is up to 134 mm.
The Canterbury mudfish, also known as the kowaro, is found only on the Canterbury Plains in New Zealand. Like other Neochanna species, it is a small, tubular and flexible fish which lacks scales. They are able to survive out of water in damp refuges if its wetland habitat dries out periodically over summer.
The waikaka or black mudfish is a fish of the family Galaxiidae, found only in swamps and wetlands in the northern half of the North Island of New Zealand, from Kaitaia in the north to the Mokau River in the south.
The brown mudfish is a galaxiid endemic to New Zealand. The species is found in wetlands in the southwest of the North Island and the northern half of the west coast of the South Island. It commonly grows to 100–130 mm in length, and it can live to at least 7 years. They are named for their brown color.
The Tasmanian mudfish, Neochanna cleaveri, is a small Australian amphidromous fish in the galaxiid family, of the order Osmeriformes.
The banded kōkopu 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 kōkopu 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.
The shortjaw kōkopu 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 kōkopu 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).
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The dwarf inanga is a galaxiid of the genus Galaxias, found in the North Island of New Zealand.
Eldon's galaxias 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.
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The torrentfish, or panoko (Māori), is an amphidromous freshwater fish that is endemic to New Zealand. Torrentfish are well adapted to life in shallow, fast-flowing riffles and rapids. They grow to a maximum of 20 cm (7.9 in) in total length, but more commonly reach 10–12 cm (3.9–4.7 in).
Gerald Stokell was a New Zealand amateur ichthyologist.
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The Whangamarino Wetland in the Waikato District is the second largest wetland complex of the North Island of New Zealand. Encompassing a total area of more than 7200 hectares, the Department of Conservation Te Papa Atawhai manages 5,923 hectares of peat bog, swamp, mesotrophic lags, open water and river systems listed as a wetland of international importance under the Ramsar Convention. Fish and Game New Zealand are the second largest landowner, managing 748 hectares of the wetland primarily as gamebird hunting habitat.
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