Cite this page as: Martin F. The species is thought to have been introduced into the Wimmera, Loddon and Campaspe river catchments in Victoria. The species is sometimes found in brackish streams and can tolerate salinities up to 50 ppt. Some populations are landlocked and others are diadromous, migrating downstream to the estuaries to spawn. Body elongate, slender; depth at vent 9. Scales absent.
|Published (Last):||21 March 2008|
|PDF File Size:||13.7 Mb|
|ePub File Size:||19.87 Mb|
|Price:||Free* [*Free Regsitration Required]|
Description[ edit ] Common galaxias have iridescent silver eyes, undersides, and gill covers, and some have an iridescent green stripe along the top of their bodies which can be intermittently seen as they swim. Their specific name maculatus "spotted" comes from the pattern of dark-mottled, leopard-like spots on an olive-brown background along their upper bodies. Common galaxias have slightly forked tails, unlike other most other galaxiids, which have square tails.
Adults are mainly found in still or slow-moving water in the lower parts of coastal streams and rivers, or around the edges of lagoons; they can tolerate a wide range of natural conditions. If oxygen levels are low as a result of eutrophication , they can jump out of the water emerse and take up oxygen through their skin as a last resort. They tend to be found in lower-elevation streams as unlike other species of Galaxias they cannot climb past waterfalls.
This species is usually considered amphidromous , a particular type of diadromy meaning that reproduction occurs in fresh water and larval growth occurs in the sea. Unless landlocked within a lake, the common galaxias spawns mainly in autumn during spring tides in the tidally influenced reaches of rivers and streams  but spawning in winter and spring has occurred. Male fish then release sperm into the water and the eggs are fertilised externally. This type of spawning is called polygynandry.
Eggs remain attached to the vegetation as the tide recedes. Environmental conditions in the vegetation particularly temperature and humidity are critical for successful egg development. Egg mortality occurs from excess exposure to sunlight, predation from mice and spiders, grazing and trampling by livestock, mowing of bankside vegetation in urban areas, and flooding. This phase of their lifecycle is little understood, as the larvae are small, transparent, and difficult to locate. The juveniles form large shoals as they move through estuaries.
Some of their life is spent in the lower reaches of rivers, where they metamorphose , before spending their adult life in suitable freshwater habitat. Some individuals return to the river they were born in natal homing , but most return to rivers other than their birth site. Males generally reach sexual maturity earlier and at a smaller size than females.
These are digenean flatworms. They are fished commercially in New Zealand, Chile, and Argentina, but the last Australian commercial fishery closed in Tasmania in the s.
For instance, in Tasmania, the adult common galaxias may only be caught using a pole of a specified maximum size 1 m. Conservation[ edit ] Galaxiid species are, in general, threatened by human activities such as intensive agriculture and land change use. These activities have removed vegetation from stream banks that are needed for spawning to protect eggs from the sun.
The increased nutrient input into streams from farming can lead to eutrophication. In New Zealand, their conservation status is declining, mostly because of habitat loss and degradation. This is the same diet as introduced trout , which not only compete for food, but also readily eat them.
In areas where trout have become naturalised, common galaxias are scarce. Common galaxias, therefore, are mostly found in stretches of streams and rivers that are less suitable for introduced trout.
Restoration[ edit ] In parts of New Zealand, this species spawning habitat has become degraded due to activities related to agriculture, urbanisation, and land use change. This creates sink populations in rivers as adult fish have nowhere suitable to lay their eggs and the majority of eggs dies. Because these sink rivers produce no eggs or larvae, a gap is created during marine dispersal.
No opportunities exist for the exchange of larvae from these sink populations with other populations. However, these sink populations can receive larvae that were born in different rivers. They will not be able to successfully reproduce and the sink cycle continues. Innovative methods to restore the riparian spawning habitat include using straw bales as a temporary replacement for vegetation.
This method ensures that eggs and larvae are produced and that each river is a source of larvae. Exclusion of livestock and fencing of the bank-side vegetation is also an effective method to encourage regrowth of suitable vegetation. Restoration of the spawning habitat helps to maintain connectivity between larvae from different rivers during marine dispersal.
They are constantly active and looking for food. They swim throughout the water column and rarely hid. Very peaceful. Seem to sleep at night. The school formed by the thirty fish we caught looks quite impressive.