Common galaxias

Common names

Common Galaxias, Inanga, Common Jollytail, Jollytail, Ika, Puyen

The common galaxias, 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.

Distribution and habitat

Common galaxias are one of the most widely distributes freshwater fish in the world and can be found around throughout New Zealand; in coastal streams in south eastern Australia, Tasmania and some parts of south west Western Australia; in Patagonia Argentina; in the Falkland Islands; and, in some Pacific Islands such as New Caledonia.

Adults mainly occur in still or slow moving water in the lower parts of coastal streams and rivers. They are also found around the edges of lakes and lagoons. It is often found in schools 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 spawns 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 larvae 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 insects, crustaceans, 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 digenean flatworms (Etchegoin et al. 2002).

Fishing

The juveniles are caught as whitebait 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).

References

• Galaxias maculatus (TSN 162129). Integrated Taxonomic Information System. Retrieved on 18 April 2006.
• "Galaxias maculatus". FishBase. Ed. Ranier Froese and Daniel Pauly. February 2006 version. N.p.: FishBase, 2006.
• Etchegoin, Jorge A.; Cremonte, Florencia & Escalante, Alicia H. (2002): Steganoderma (Steganoderma) valchetensis n. sp. (Digenea: Zoogonidae) from the relict fish Gymnocharacinus bergi (Osteichthyes: Characidae) in Argentina. Systematic Parasitology 51(2): 149–153. doi: 10.1023/A:1014098732668 (HTML abstract)

External links

• Native Fish Australia
• http://www.niwascience.co.nz/rc/freshwater/fishatlas/species/inanga NIWA June 2006