Spotted galaxias (''Galaxias truttaceus'') is a largish, primarily-freshwater
galaxias species found in southern
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. They are a somewhat tubular, deep-bodied fish, with a dusky brownish-red colouration overlain with dark, haloed spots, dramatic black edges to
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
The fus ...
,
anal
Anal may refer to:
Related to the anus
*Related to the anus of animals:
** Anal fin, in fish anatomy
** Anal vein, in insect anatomy
** Anal scale, in reptile anatomy
*Related to the human anus:
** Anal sex, a type of sexual activity involving ...
and
pelvic fin
Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...
s, and a dark diagonal stripe through the eye.
Distribution
Spotted galaxias has a very wide distribution, being found in southern
Victoria, all of
Tasmania
Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...
, offshore islands in between, as well as
south-west Western Australia
Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...
.
On the mainland spotted galaxias is generally recognised as a freshwater fish species with a marine larval phase (larvae are swept out to sea and return to freshwater habitats as early stage juveniles), and thus only found in coastal rivers. Spotted galaxias are generally found in coastal rivers in Tasmania as well, however natural landlocked populations do occur in some freshwater lakes in Tasmania.
Spotted galaxias were assumed not to be native to the
Murray-Darling river system, however records of native fish fauna compiled by
William Blandowski
Johann Wilhelm Theodor Ludwig von Blandowski, known as William Blandowski (21 January 1822 – 18 December 1878), was a German explorer, soldier, zoologist and mining engineer of Polish descent, famous for his exploration of the Murray and Darlin ...
in the 1850s suggest the species did historically occur there. This may cause a re-evaluation of the spotted galaxias specimens occasionally recovered in the Murray-Darling river system, which until now were assumed to be accidental translocations via the
Snowy Mountains Hydro-Electric Scheme
The Snowy Mountains Scheme, also known as the Snowy Hydro or the Snowy scheme, is a hydroelectricity and irrigation in Australia, irrigation complex in south-east Australia. Near the border of New South Wales and Victoria (Australia), Victoria, ...
.
In Western Australia, spotted galaxias are limited to the
Goodga,
Angove, and
Kent
Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...
river catchments on the southern coast. All three catchments drain to coastal lakes which are only connected to the ocean during the winter season in wet years.
[
]
Habitat, diet, and reproduction
Spotted galaxias, in their juvenile and adult stages, inhabit coastal rivers at low to medium altitude. They prefer cool, flowing rivers in forested catchments with excellent riparian vegetation, good water quality and cover in the form of boulders, sunken logs and overhanging banks.
Spotted galaxias are a predatory fish, feeding in the currents or "drift" similar to exotic trout
Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...
species. Their diet consists mainly of aquatic and terrestrial invertebrates.
Spawning occurs in winter in rivers. Larvae are swept out to sea and return and migrate back up rivers as early-stage juveniles which initially do not resemble adult fish. Returning juveniles are sometimes intercepted by humans as whitebait, and were severely overfished in previous decades. Landlocked lake populations spawn in spring.
Human use
Before the introduction of exotic trout
Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...
species to Australia, an introduction that has caused severe problems for the conservation of Australian native fish, spotted galaxias were keenly fished for by early Australian anglers using fly-fishing gear. The species was appreciated for its beauty, its willingness to take wet and dry flies, its game fighting ability on very light tackle, and its relatively large size by galaxias standards, sometimes reaching 30 cm, and commonly 20 cm. (Spotted galaxias appear to have had a larger average size before the introduction of exotic trout species.) A handful of fly-fishers in Australia are now re-discovering the pleasure of fly-fishing for this magnificent native fish with ultra-light fly-fishing tackle.
As mentioned above, early-stage juveniles returning to estuaries were and sometimes still are netted as white bait, which are caught for human consumption.
With their beautiful appearance spotted galaxias have potential as aquarium fish, but do require cool water.
Conservation
Spotted galaxias are threatened by dams and weirs blocking migration and fragmenting river habitats, irresponsible forestry and farming practices that degrade river environments through siltation and other effects, and competition and predation by exotic trout species.
In Tasmanian rivers spotted galaxias numbers are severely depressed when exotic trout species are present (Ault & White, 1994). This is a common phenomena; galaxias species that manage to survive the presence of exotic trout (many species do not) such as spotted galaxias are forced into sub-optimal feeding locations, feeding times and diets by aggressive competition from exotic trout species (McDowall, 2006). Galaxias populations in such situations tend to display lower than normal growth, size and fecundity, raising concerns for their long-term future (McDowall, 2006).
In southern Victoria however many recreational fishermen report that spotted galaxias are found only in the few trout-free streams remaining. Spotted galaxias appear to reach a larger maximum size in these few trout-free streams than in Tasmania. A lack of exotic-trout-free habitat reserved for spotted galaxias and other native fish species in south-eastern Australia generally is a major concern.
References
*
*
* Ault, T.R. and White, R.W.G. (1994) Effects of habitat structure and the presence of brown trout on the population density of ''Galaxias truttaceus'' in Tasmania, Australia. ''Transactions of the American Fisheries Society'' 123: 939–949.
*McDowall, R.M. (ed.) (1996) ''Freshwater fishes of south-eastern Australia.'' Reed Books, Sydney.
*McDowall, R.M. (2006) Crying wolf, crying foul, or crying shame: alien salmonids and a biodiversity crisis in the southern cool-temperate galaxioid fishes? ''Rev Fish Biol Fisheries'' 16: 233–422.
References
External links
Spotted Galaxias video on Youtube
Native Fish Australia – Spotted galaxias page
{{Taxonbar, from=Q5253409
Galaxias
Freshwater fish of Australia
Taxa named by Achille Valenciennes
Fish described in 1846