Common galaxias
Encyclopedia
The common galaxias or the inanga (Galaxias maculatus), is a species
of fish
from the galaxiid
family that is very widespread in the southern hemisphere
. It is a slim narrow fish with a forked tail and as an adult it lives in freshwater rivers and lakes. Common galaxias grows to a length of 40 to 120 mm, but can grow up to 180 mm. The English vernacular names used for the species also include cowfish, jollytail, common jollytail, eel gudgeon, lananga, native trout, pulangi, slippery tarki, spotted minnow and whitebait.
; in coastal streams in south eastern Australia
, Tasmania
and some parts of south west Western Australia
; in Chile (From 35°S to 55S°), Patagonia
, Argentina
; in the Falkland Islands
; and, in some Pacific Islands
such as New Caledonia
.
Adults are mainly found in still or slow moving water in the lower parts of coastal streams and rivers, or around the edges of lakes and lagoons. They are often found in schools
that are not very large. They can tolerate a wide range of natural conditions.
downstream in rivers and streams amongst vegetation on the banks of the estuary
regions during a spring tide mainly in autumn. The eggs remain on the bank (out of the water) until the next spring tide when they hatch into larva
e which are swept out to the ocean. For the next 5–6 months the larvae live in the sea and develop into juvenile fish, often referred to as whitebait
. When they are about 30 mm in length and 3–4 mm in width they swim up a river on the incoming tide until they reach a suitable habitat where they develop into the adult form. As adults they eat insect
s, crustacean
s, and molluscs. In other words they share the diet of introduced trout
. Indeed introduced trout are a major threat to these fish and in areas where introduced Trout has become naturalised galaxias are scarce. Introduced Trout not only compete for food but also readily eat this species. Common galaxias, therefore, are mostly found in stretches of streams and rivers that are not suitable for introduced trout.
This species lives for about twelve months and usually dies after spawning.
In New Zealand, Deretrema philippae (=Limnoderetrema minutum) is known to parasitize the intestine
(and possibly gall bladder) of the common galaxias. Similarly, the intestinal parasite
Steganoderma szidati has been reported from this species' Argentinian population. These are digenea
n flatworm
s (Etchegoin et al. 2002).
while moving upstream and are much valued as a delicacy leading to their protection with licensing and controlled fishing seasons in order to preserve adult populations. Fishing may be both for recreational and commercial activity depending on the geographic location and size of the populations.
Some jurisdictions permit fishing of the adults but again under regulation or licence in order to preserve the adult population but others ban it altogether unless the fisher belongs to an indigenous people (e.g., New Zealand
Māori). For instance, in Tasmania
, the adult common galaxias may only be caught using a pole of a specified maximum size (one metre).
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
from the galaxiid
Galaxiid
The Galaxiidae, also known by the anglicised name as galaxiids, are a family of mostly small freshwater fish in the southern hemisphere. The majority of species live in Australia or New Zealand, some are also found in South Africa, South America, Lord Howe Island, New Caledonia and the Falkland...
family that is very widespread in the southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
. It is a slim narrow fish with a forked tail and as an adult it lives in freshwater rivers and lakes. Common galaxias grows to a length of 40 to 120 mm, but can grow up to 180 mm. The English vernacular names used for the species also include cowfish, jollytail, common jollytail, eel gudgeon, lananga, native trout, pulangi, slippery tarki, spotted minnow and whitebait.
Distribution and habitat
Common galaxias are one of the most widely distributed freshwater fish in the world and can be found around throughout New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
; in coastal streams in south eastern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
and some parts of south west Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
; in Chile (From 35°S to 55S°), Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
; in the Falkland Islands
Falkland Islands
The Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...
; and, in some Pacific Islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
such as New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
.
Adults are mainly found in still or slow moving water in the lower parts of coastal streams and rivers, or around the edges of lakes and lagoons. They are often found in schools
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
that are not very large. They can tolerate a wide range of natural conditions.
Life history
Unless within a lake which is landlocked, the common galaxias spawnsSpawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
downstream in rivers and streams amongst vegetation on the banks of the estuary
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
regions during a spring tide mainly in autumn. The eggs remain on the bank (out of the water) until the next spring tide when they hatch into larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e which are swept out to the ocean. For the next 5–6 months the larvae live in the sea and develop into juvenile fish, often referred to as whitebait
Whitebait
Whitebait is a collective term for the immature fry of fish, typically between 25 and 50 millimetres 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...
. When they are about 30 mm in length and 3–4 mm in width they swim up a river on the incoming tide until they reach a suitable habitat where they develop into the adult form. As adults they eat insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, and molluscs. In other words they share the diet of introduced trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
. Indeed introduced trout are a major threat to these fish and in areas where introduced Trout has become naturalised galaxias are scarce. Introduced Trout not only compete for food but also readily eat this species. Common galaxias, therefore, are mostly found in stretches of streams and rivers that are not suitable for introduced trout.
This species lives for about twelve months and usually dies after spawning.
In New Zealand, Deretrema philippae (=Limnoderetrema minutum) is known to parasitize the intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
(and possibly gall bladder) of the common galaxias. Similarly, the intestinal parasite
Intestinal parasite
Intestinal parasites are parasites that populate the gastro-intestinal tract in humans and other animals. They can live throughout the body, but most prefer the intestinal wall. Means of exposure include: ingestion of undercooked meat, drinking infected water, and skin absorption...
Steganoderma szidati has been reported from this species' Argentinian population. These are digenea
Digenea
Digenea is a subclass within the Platyhelminthes consisting of parasitic flatworms with a syncytial tegument and, usually, two suckers, one ventral and one oral. Adults are particularly common in the digestive tract, but occur throughout the organ systems of all classes of vertebrates...
n flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
s (Etchegoin et al. 2002).
Fishing
The juveniles are caught as whitebaitWhitebait
Whitebait is a collective term for the immature fry of fish, typically between 25 and 50 millimetres 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...
while moving upstream and are much valued as a delicacy leading to their protection with licensing and controlled fishing seasons in order to preserve adult populations. Fishing may be both for recreational and commercial activity depending on the geographic location and size of the populations.
Some jurisdictions permit fishing of the adults but again under regulation or licence in order to preserve the adult population but others ban it altogether unless the fisher belongs to an indigenous people (e.g., New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
Māori). For instance, in Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
, the adult common galaxias may only be caught using a pole of a specified maximum size (one metre).
External links
- Native Fish Australia
- http://www.niwascience.co.nz/rc/freshwater/fishatlas/species/inanga NIWA June 2006