Australian bass
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| Macquaria novemaculeata (Steindachner, 1866) |
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[edit] Taxonomy
The Australian bass (Macquaria novemaculeata) is an Australian native fish in the Percichthyidae family and Macquaria genus that occurs in coastal rivers and streams along the east coast of Australia. It is an important member of the fish assemblages found in east coast river systems and a popular angling species.
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.
[edit] Description and Size
Australian bass have a moderately deep, elongated body that is laterally compressed. They have a forked caudal fin and angular anal and soft dorsal fins. 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. The operculum or gill cover on Australian bass carry extremely sharp spines that can cut fishermens' fingers deeply.
Australian bass vary in colour 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, overall, a smallish species, averaging in most waters around 0.5 kg and 20–30 cm. A fish of 1 kg or larger is a good specimen. Maximum size appears to be around 2.5 kg and 55 cm in southern waters, and around 3.0 kg and 60–65 cm in northern waters.
Typically, Australian bass stocked in man-made impoundments (where they cannot breed) show greater average and maximum sizes than wild river fish.
[edit] Range
The range of Australian bass extends 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 largely a freshwater species, but must breed in estuarine waters. Consequently, Australian bass are highly 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.
[edit] Diet
Australian bass have a diet of terrestrial insects (particularly cicadas), aquatic invertebrates including (particularly) shrimps and prawns, 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.
[edit] Growth and Reproduction
For reasons that are not clear, Australian bass are extremely slow growing. Australian bass continue the trend present in the larger native fish species of SE Australia of being very 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.
As with other Macquaria species, there is sexual dimorphism in Australian bass. Males have an absolute maximum size of 1.0 kg or less, while females regularly exceed 1.0 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).
Australian bass spawn 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). Australian 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. Australian 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.
[edit] Conservation
Wild Australian 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.
[edit] Fishing
Fishing for Australian bass is generally a summertime affair, undertaken during the warmer months in the freshwater reaches of the rivers they inhabitat. Australian bass are keenly fished for as they are an outstanding sportsfish, astonishingly fast and powerful for their size. Bass in their natural river habitats are not to be underestimated; they head straight for the nearest snags (sunken timber) when hooked and light but powerful tackle and stiff drag settings are needed to stop them.
During the day Australian bass generally remain close to cover (e.g. snags, overhanging trees), and small plug lures and flies cast close to such cover are used. At night bass are a roaming pelagic feeder and surface lures (which waddle across the surface of the water) are used. The large and sudden explosion a good bass makes when taking a surface lure is guaranteed to the give the fisherman a fright!
It pays for fishermen to remember that wild Australian bass are highly migratory when in the freshwater reaches of rivers.
Australian bass fishermen almost exclusively practice catch and release, which is necessary for the preservation of wild bass stocks. The use of barbless hooks (which can be created by crushing the barbs flat with a pair of needle-nosed pliers) is essential as bass hit lures with great ferocity and are consequently almost impossible to unhook on barbed hooks. Conversely, bass are swiftly and easily released if barbless hooks are used.
Responsible fishermen now tend to avoid fishing for Australian bass in estuaries in winter, so that the species can spawn in peace.
[edit] References
- Macquaria novemaculeata (TSN 641898). Integrated Taxonomic Information System. Accessed on 11 March 2006.
- "Macquaria novemaculeata". FishBase. Ed. Ranier Froese and Daniel Pauly. 10 2005 version. N.p.: FishBase, 2005.
