| Australian Bass |
Article Index for Australian |
Website Links For Australian |
Information AboutAustralian Bass |
| CATEGORIES ABOUT AUSTRALIAN BASS | |
| percichthyidae | |
| freshwater fish of australia | |
The Australian Bass, '''''Macquaria novemaculeata''''' is a species of Fish in the family Percichthyidae that occurs in coastal waterways along the east coast of Australia , from east of Wilson's Promontory in Victoria east and north along the eastern seaboard to the rivers and creeks of the Bundaberg region in central Queensland . Australian Bass are a freshwater species, but one that must breed in estuarine waters. Consequently, Australian Bass are migratory, and reside in freshwater for the warmer half of the year or slightly more and the estuarine reaches in Winter . For this reason Australian Bass do not naturally occur in the Murray - Darling river system, which, although extensive, has only one entrance to the sea on Australia's southern coastline. Australian Bass are closely related and very similar in appearance to Estuary Perch (''Macquaria colonorum''). Estuary Perch however tend to remain in the estuarine reaches or (occasionally) the extreme lower freshwater reaches. DESCRIPTION Australian Bass are, overall, a smallish species, averaging in most waters around 0.5 kg and 20–25 cm. A fish of 1 kg or larger is a good specimen. Maximum size appears to be around 2.5 kg and 50 cm in southern waters, and around 3.0 kg and 60 cm in northern waters. Australian Bass are a small to medium fish with a moderately deep, elongated body and laterally compressed. They have a forked Caudal Fin and angular Anal and soft Dorsal Fin s. Their spiny dorsal fin is of medium height and strong. They have a medium sized mouth and relatively large eyes than can appear dark in low light or red in bright light. As with other ''Macquaria'' species, there is Sexual Dimorphism . Males have an absolute maximum size of 1.0 kg or less, while females regularly exceed 1 kg and sometimes reach the maximum size of 2.5–3.0 kg. Females reach sexual maturity at older, larger sizes than males. Research also suggests there is sexual segregation in the summer, non-spawning season for resource partitioning purposes. Research suggests males inhabit the lower freshwater reaches while females extend significantly into the freshwater reaches, to an altitudinal limit of around 600 metres (if there are no natural or man-made obstructions). Typically, Australian Bass stocked in man-made impoundments (where they cannot breed) show greater average and maximum sizes than wild river fish. Australian Bass vary from gold in clear sandy streams to the more usual bronze or bronze-green colouration in streams with darker substrates and/or some tannin staining to the water. Australian Bass are keenly fished for as they are an amazing sportsfish, incredibly fast and powerful for their size. Australian Bass have a diet of terrestrial Insect s (particularly Cicada s), aquatic Invertebrate s including (particularly) Shrimp s and Prawn s, and small fish. Any small creature that swims across a Bass pool such as a Mouse , Lizard or Frog is at risk of being taken by a large Bass. Australian Bass breed in Estuaries in winter, in the months of July or August, in salinities of 12 to 18 ppt (1/3 to 1/2 that of seawater). Bass are highly fecund, usually producing several hundred thousand eggs with very large fish recorded as producing over 1,000,000 eggs. The eggs are demersal and estuarine vegetation such as sea grass may be important in "trapping" and protecting eggs. Bass breed in estuaries, but they still appear to rely on strong freshes or small floods coming down river systems and into the estuaries at time of hatching and first feeding for strong survival and recruitment of Bass larvae. Juvenile Bass migrate into the freshwaters reach after spending a month or two in estuarine waters. Australian Bass continue the trend of native fish of SE Australia being incredibly long-lived. Longevity is a survival strategy to ensure that most adults participate in at least one exceptional spawning and recruitment event, which are often linked to unusually wet ' La Niña ' years and may only every one or two decades. Maximum recorded age is 22 years. CONSERVATION Wild Bass stocks have declined seriously, from stream siltation and other forms of habitat degradation, and particularly through dams and weirs. If Bass are prevented from migrating to estuaries for breeding by an impassable dam or weir, then they will die out above that dam or weir. Some dams or weirs exclude Bass from the vast majority of their habitat. It is estimated for example that Tallowa Dam on the Shoalhaven River , once a Bass stronghold, currently excludes wild Bass from more than 80% of their former habitat. Hatchery breeding and stocking of Bass is used to create fisheries above dams and weirs but these are causing concern over genetic diversity issues, use of Bass broodfish from different genetic strains, and introduction/translocation of unwanted pest fish species in stockings. REFERENCES EXTERNAL LINKS |
|
|