Eldon's galaxias (''Galaxias eldoni'') is an endangered

galaxiid 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 ...

fish endemic to

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. One of several fishes in the genus ''

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

'' found in Central Otago, it has a very small home range and is at risk of being driven to extinction by

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...

introduced for recreational fishing.

Taxonomy

Eldon's galaxias was described in 1997 by New Zealand freshwater ichthyologist

Bob McDowall Robert (Bob) Montgomery McDowall (15 September 1939 – 20 February 2011) was one of New Zealand's most prominent freshwater ichthyologists. Biography McDowall was born on 15 September 1939, the son of dairy scientist Frederick Henry 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. The name recognises the ichthyologist G. A. (Tony) Eldon, who helped collect specimens and had retired not long before McDowall described this species.

Description

Eldon's galaxias (Galaxias eldoni) - closeup of skin

''Galaxias eldoni'' is an elongated, deep-bodied ''Galaxias'', usually 80 mm in length (although very large individuals can reach 155 mm). 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). Unlike all other ''Galaxias'' (except '' G. divergens)'', it has only 15

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

rays and no

pyloric caeca Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish a ...

Habitat and distribution

Eldon's galaxias (Galaxias eldoni) habitat

This species lives only in eastern waterways of Otago, in wetlands and small streams that flow into the Taieri,

Tokomairiro Milton, formerly known as Tokomairiro or Tokomairaro, is a town of over 2,000 people, located on State Highway 1, 50 kilometres to the south of Dunedin in Otago, New Zealand. It lies on the floodplain of the Tokomairaro River, one branch of whi ...

and

Waipori Waipori may refer to either: * Waipori, New Zealand, a township within Dunedin, New Zealand's city limits * The Waipori River in Otago in the South Island of New Zealand, or to * Lake Waipori, an area of wetlands draining into the Waipori River ...

rivers and below

Lake Mahinerangi Lake Mahinerangi is a lake formed when a dam was built on the Waipori River for hydroelectricity, hydroelectric generation. The lake is to the west of Dunedin in New Zealand's South Island. Construction of the dam started in 1903 and since 1907, ...

. 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. It is a relatively good climber, able to wriggle up wet rocky slopes, and is able to negotiate waterfalls up to 3 m high. 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. 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.

Feeding

''Galaxias eldoni'' feeds on small freshwater invertebrates such as stoneflies and

mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order ...

. They will also feed on larger prey like freshwater crayfish/ kōura, and food that is carried by the current.

Life cycle

Unlike the more well-known '

whitebait Whitebait is a collective term for the immature fry of fish, typically between long. Such young fish often travel together in schools along coasts, and move into estuaries and sometimes up rivers where they can be easily caught using fine- ...

' ''Galaxias'' species, ''G. eldoni'' is not

diadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

; 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. 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

riffle A riffle is a shallow landform in a flowing channel. Colloquially, it is a shallow place in a river where water flows quickly past rocks. However, in geology a riffle has specific characteristics. Topographic, sedimentary and hydraulic indica ...

s, and eggs are laid directly into the stony stream bottom. 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.

Conservation

Eldon's galaxias (Galaxias eldoni) electrofishing

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

. Since the species was described in 1997 several small populations have been driven extinct from conversion of land to forestry or farming. The building of irrigation canals has allowed the closely related species ''Galaxias pullus'' to invade its range and hybridise with it. Currently there are protected areas for this species in the

Lammerlaw Range The Lammerlaw Range is in the Otago region of New Zealand. It is an important watershed, and the source of many of the tributaries in the Taieri and lower Clutha River systems. The origins of the placename are Scottish. Windfarms have been site ...

, but they are vulnerable to being invaded by trout, or trout being deliberately introduced.

References

External links

*Eldon's galaxias discussed on RNZ ''Critter of the Week''
4 August 2017
{{Taxonbar, from=Q5254084

Eldon's galaxias 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 ...

Endemic freshwater fish of New Zealand Fish of the South Island Taxa named by Bob McDowall