Australian bass
Encyclopedia
Australian bass are a small to medium sized, primarily freshwater (but estuarine spawning) native fish
found in coastal rivers and streams along the east coast of Australia
. They are a member of the Percichthyidae family and, currently, the Macquaria
genus. Australian bass are an iconic, highly predatory native fish. They are an important member of the native fish faunas found in east coast river systems and an extremely popular angling species.
Australian bass (Macquaria novemaculeata) 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.
As their scientific names indicate, Australian bass and estuary perch are currently placed in the Macquaria
genus — one of a number of Australian genera in the Percichthyidae family — along with two species of native perch from the Murray-Darling Basin, golden perch
(Macquaria ambigua) and Macquarie perch
(Macquaria australasica). This revision to their taxonomy occurred in the late 1970s. Prior to that, Australian bass and estuary perch were placed in a separate genus, Percalates. Results from recent research using genetic MtDNA analysis indicate Australian bass and estuary perch do belong in a separate genus to golden perch and Macquarie perch, and this may result in them being put back into a resurrected Percalates genus. A rather surprising and unexpected finding of this research is that the putative Percalates genus (i.e. Australian bass and estuary perch) appears to be genetically closer to the Maccullochella
genus (i.e. Murray cod
and other cod species) than the remnant Macquaria genus is (i.e. golden perch and Macquarie perch).
The specific name for Australian bass — novemaculeata — coined by Steindachner when he scientifically described and named the species, translates literally from the Latin as "new" (novem) and "spotted" (maculeata), and refers to the distinct black blotches juvenile bass are marked with when very small (i.e. <6–7 cm).
s. Their spiny dorsal fin
is of medium height, strong and sharp. They have a medium sized mouth and relatively large eyes than can appear dark in low light or red in bright light. The opercula
or gill covers on Australian bass carry extremely sharp flat 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-sized species, averaging in most waters around 0.4–0.5 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.
in Victoria
east and north along the eastern seaboard to the rivers and creeks of the Bundaberg region in central Queensland
.
Australian bass are not found in the Murray-Darling system
because although the system is extensive, it has only one variable entrance to the Southern Ocean, a feature that appears to be incompatible with the estuarine breeding habits of Australian bass and other aspects of their life cycle.
A general description of the migratory pattern for adult Australian bass would be:
Obviously the timing of these migratory movements varies slightly from the south to the north of their range. The timing of these migratory movements are also dependent on river flows, particularly freshes and floods that drown out and make larger rapids and cascades passable.
Australian bass are found at their highest altitude in the freshwater reaches of rivers during the months of December, January and February. Research indicates there is sexual segregation in this non-spawning season for resource partitioning purposes. Males inhabit the lower freshwater reaches of rivers while females travel far into the middle and upper freshwater (upland
) reaches, up to an altitudinal limit of around 600 metres (if there are no natural or man-made obstructions). For instance, Australian bass originally migrated up to the Dalgety
region in the Snowy River
, well above Oallen Crossing on the Shoalhaven River
and far up the Warragamba River
and Coxs River before these rivers were dammed.
Australian bass are strong swimmers at all sizes and can easily traverse rapids and fast-flowing water. However, they generally avoid sitting directly in currents to conserve energy.
At night Australian bass display pelagic (“near-surface”) behaviour and actively hunt prey in shallow water and at the water's surface.
When aggregated for spawning in the broad reaches of estuaries in winter, Australian bass are less cover oriented, and generally sit in deeper water.
However, Australian bass are fierce predators and any small creature that swims across a bass pool such as (introduced) mice
and native lizard
s or frog
s are at risk of being taken by a large Australian bass, and are regularly taken.
As with other Macquaria
species, there is sexual dimorphism
in Australian bass. Males tend to 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. Males reach sexual maturity at around 3–4 years of age, females at 5–6 years of age.
in winter, generally in the months of July or August.
The salinity range in which Australian bass spawn is still not clear. Estuaries are dynamic habitats with daily fluxes in salinity due to tides, and are also affected by droughts, floods and freshes (minor, temporary rises in flow), making measurements of preferred spawning salinities for wild Australian bass difficult.
Australian bass spawn in salinities of 8–12 parts per thousand (salt water is approximately 36 ppt), based on capture of recently spawned larval and juvenile Australian bass in estuaries. Australian bass sperm have no viability at or below 6 ppt, but are most viable at 12 ppt, the latter probably being the most relevant fact. However, it has been reported that Australian bass spawned in salinities of 12–18 ppt, with this statement based on fishermens' reports of observing wild Australian bass spawnings and some unpublished data gathered by the NSW Fisheries Department.
Artificial breeding of Australian bass is carried out at much higher salinities than natural.
Australian bass are highly fecund, with a reported mean fecundity ("fertility") of 440,000 eggs from the mature wild female specimens examined, and one very large specimen yielding 1,400,000 eggs. The eggs are reported as being demersal ("sinking") in natural spawning salinities, in which case estuarine vegetation such as sea grass almost certainly play an important role in "trapping" and protecting eggs. Larvae hatch in 2–3 days. Juvenile Australian bass migrate into the freshwater reaches after spending several months in estuarine waters.
Despite spawning in estuaries, Australian bass rely on floods coming down river systems into the estuaries throughout the winter period, both to stimulate migration and spawning in adult Australian bass and for strong survival and recruitment of Australian bass larvae.
Australian bass adults and larvae may also enter the sea (the latter perhaps involuntarily) during winter spawning in times of flood. It has been reported:
This kind of movement leads to some genetic interchange between river systems and is important in maintaining a high degree of genetic homogeneity ("sameness") in Australian bass stocks and preventing speciation
. However, this movement has not prevented distinct genetic profiles and subtle morphological ("body shape") differences developing in different river systems. These findings indicate it is important to use the appropriate regional Australian bass stocks for artificial breeding and stocking projects.
Dams and weirs blocking migration of Australian bass both to estuaries and to the upper freshwater reaches of coastal rivers is the most potent cause of decline. Most coastal rivers now have dams and weirs on them. If Australian 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 Australian bass from the vast majority of their habitat. It is estimated for example that Tallowa Dam on the Shoalhaven River
, once an Australian bass stronghold, currently excludes wild Australian bass from more than 80% of their former habitat (in early 2010 however a "fish lift" was fitted to the dam). Dams and weirs also diminish or completely remove flood events required for effective breeding of adult bass and effective recruitment of juvenile Australian bass. A related issue is the myriad of other structures on coastal rivers such as poorly designed road crossings that (often needlessly) block migration of Australian bass.
Another potent cause of decline is habitat degradation. Unfortunately poor land management practices have been the norm historically in Australia. Complete clearing of riparian (river bank) vegetation, stock trampling river banks, and massive siltation from these poor practices as well as poor practices in the catchment, can severely degrade and silt coastal rivers to the point of being uninhabitable for Australian bass. The Bega River
in southern New South Wales
is a particularly salutory example of a coastal river so stripped of riparian vegetation and so silted with coarse granitic sands from poor land management practices, that the majority of it is now completely uninhabitable by Australian bass and other native fish.
As a slow-growing fish, Australian bass are vulnerable to overfishing, and overfishing has been a driver of decline in Australian bass stocks in past decades. However, the situation has improved markedly now the majority of fishermen are practicing catch and release
with Australian bass.
Hatchery breeding and stocking of Australian 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. Stockings can also mask and divert attention away from serious habitat degradation and decline of wild stocks in catchments.
s (sunken timber) when hooked and light but powerful tackle and stiff drag settings are needed to stop them.
As mentioned above, during the day Australian bass generally remain close to or in cover (e.g. snags, overhanging trees), and small plug lures and flies
cast close to such cover are used. In recent years fly fishing
for Australian bass using surface flies imitating cicadas has proven to be extremely effective. At night Australian bass are a roaming pelagic feeder and surface lure
s (which waddle or fizz across the surface of the water) are used. The large and sudden explosion a good Australian bass makes when taking a surface lure is guaranteed to the give the fisherman a fright!
Some of the best Australian bass fishing is coastal rivers and tributaries where access is difficult. Fishing these more remote locations can be extremely rewarding both for the fishing and the scenery. Fishing the more remote bass water is therefore usually the domain of the hardened backpacking fisherman or the dedicated kayak fisherman willing to drag his kayak over numerous logs and other obstacles.
It pays for fishermen to remember that wild Australian bass are still a highly migratory when in the freshwater reaches of rivers, and can also be an extremely wary fish in these habitats, much more so than exotic trout species.
Australian bass fishermen almost exclusively practice catch and release
, which is necessary for the preservation of wild Australian 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 Australian bass hit lures with great ferocity and are consequently almost impossible to unhook on barbed hooks. Conversely, Australian bass are swiftly and easily released if barbless hooks are used.
Responsible fishermen now avoid fishing for wild Australian bass in estuaries in winter, so that this increasingly pressured native fish can spawn in peace. In late July 2007 the NSW Fisheries Department announced a new closed season for Australian bass and estuary perch, from 1 June to 31 August.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
found in coastal rivers and streams along the east coast of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. They are a member of the Percichthyidae family and, currently, the Macquaria
Macquaria
The Macquaria genus is a genus of medium-sized, predatory native fish in the Percichthyidae family. The Macquaria genus was created by merging the old genera Plectrotripes and Macquaria and Percalates...
genus. Australian bass are an iconic, highly predatory native fish. They are an important member of the native fish faunas found in east coast river systems and an extremely popular angling species.
Taxonomy
Estuary perch
The estuary perch, Macquaria colonorum, is an Australian species of the Percichthyidae family.It is very similar to and very closely related to its sister species the Australian bass, Macquaria novemaculeata...
(Macquaria colonorum). Estuary perch however tend to remain in the estuarine reaches or (occasionally) the extreme lower freshwater reaches.
As their scientific names indicate, Australian bass and estuary perch are currently placed in the Macquaria
Macquaria
The Macquaria genus is a genus of medium-sized, predatory native fish in the Percichthyidae family. The Macquaria genus was created by merging the old genera Plectrotripes and Macquaria and Percalates...
genus — one of a number of Australian genera in the Percichthyidae family — along with two species of native perch from the Murray-Darling Basin, golden perch
Golden perch
The golden perch, Macquaria ambigua, is an Australian native freshwater fish, primarily of the Murray-Darling river system. It is not a true perch of the genus Perca....
(Macquaria ambigua) and Macquarie perch
Macquarie perch
The Macquarie perch is an Australian native freshwater fish of the Murray-Darling river system. It is a member of the Percichthyidae family and is closely related to the golden perch ....
(Macquaria australasica). This revision to their taxonomy occurred in the late 1970s. Prior to that, Australian bass and estuary perch were placed in a separate genus, Percalates. Results from recent research using genetic MtDNA analysis indicate Australian bass and estuary perch do belong in a separate genus to golden perch and Macquarie perch, and this may result in them being put back into a resurrected Percalates genus. A rather surprising and unexpected finding of this research is that the putative Percalates genus (i.e. Australian bass and estuary perch) appears to be genetically closer to the Maccullochella
Maccullochella
Maccullochella is a genus of large Australian predatory freshwater fish within the Percichthyidae family. The Maccullochella genus was named after an early Australian fish researcher with the surname McCulloch....
genus (i.e. Murray cod
Murray Cod
The Murray cod is a large Australian predatory freshwater fish of the Maccullochella genus and the Percichthyidae family. Although the species is a called cod in the vernacular, it is not related to the northern hemisphere marine cod species...
and other cod species) than the remnant Macquaria genus is (i.e. golden perch and Macquarie perch).
The specific name for Australian bass — novemaculeata — coined by Steindachner when he scientifically described and named the species, translates literally from the Latin as "new" (novem) and "spotted" (maculeata), and refers to the distinct black blotches juvenile bass are marked with when very small (i.e. <6–7 cm).
Description and size
Australian bass have a moderately deep, elongated body that is laterally compressed. They have a forked caudal ("tail") fin and angular anal and soft dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s. Their spiny dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is of medium height, strong and sharp. They have a medium sized mouth and relatively large eyes than can appear dark in low light or red in bright light. The opercula
Operculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
or gill covers on Australian bass carry extremely sharp flat 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-sized species, averaging in most waters around 0.4–0.5 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.
Range
Australian bass are found in coastal rivers and streams from Wilsons PromontoryWilsons Promontory
Wilsons Promontory is a peninsula that forms the southernmost part of the Australian mainland and is located at . South Point at is the southernmost tip of Wilsons Promontory and hence of mainland Australia...
in Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
east and north along the eastern seaboard to the rivers and creeks of the Bundaberg region in central Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
.
Australian bass are not found in the Murray-Darling system
Murray-Darling Basin
The Murray-Darling basin is a large geographical area in the interior of southeastern Australia, whose name is derived from its two major rivers, the Murray River and the Darling River. It drains one-seventh of the Australian land mass, and is currently by far the most significant agricultural...
because although the system is extensive, it has only one variable entrance to the Southern Ocean, a feature that appears to be incompatible with the estuarine breeding habits of Australian bass and other aspects of their life cycle.
Migratory patterns
Australian bass are primarily a freshwater riverine species, but must breed in estuarine waters. Consequently, Australian bass reside in the freshwater reaches of coastal rivers for the warmer half of the year or slightly more and the estuarine reaches in winter, and are highly migratory in general.A general description of the migratory pattern for adult Australian bass would be:
- September: re-enter lower freshwater reaches after spawning
- October–November: movement through middle freshwater reaches
- December–February: maximum penetration into negotiable upper freshwater reaches
- March–April: slow movement back down through freshwater reaches in anticipation of spawning run
- May: strong spawning run to estuarine reaches
- June–July–August: aggregation and spawning in estuarine reaches
Obviously the timing of these migratory movements varies slightly from the south to the north of their range. The timing of these migratory movements are also dependent on river flows, particularly freshes and floods that drown out and make larger rapids and cascades passable.
Upland and lowland (freshwater ecology)
In studies of the ecology of freshwater rivers, habitats are classified as upland and lowland.-Definitions:Upland habitats are cold, clear, rocky, fast flowing rivers in mountainous areas; lowland habitats are warm, slow flowing rivers found in relatively flat lowland areas, with water that is...
) reaches, up to an altitudinal limit of around 600 metres (if there are no natural or man-made obstructions). For instance, Australian bass originally migrated up to the Dalgety
Dalgety, New South Wales
Dalgety is a small town in New South Wales Australia, on the banks of the Snowy River between Melbourne and Sydney.The town is located at what was once an important river crossing along the Travelling Stock route from Gippsland to the Snowy Mountains High Country dating from the 1840s.- History...
region in the Snowy River
Snowy River
The Snowy River is a major river in south-eastern Australia. It originates on the slopes of Mount Kosciuszko, Australia's highest mainland peak, draining the eastern slopes of the Snowy Mountains in New South Wales, before flowing through the Snowy River National Park in Victoria and emptying into...
, well above Oallen Crossing on the Shoalhaven River
Shoalhaven River
The Shoalhaven River is a river rising from the Southern Tablelands and flowing into the ocean near Nowra on the South Coast of New South Wales, Australia.- History :...
and far up the Warragamba River
Warragamba River
The Warragamba River is a tributary of the Nepean River, and hence of the Hawkesbury River, in New South Wales, Australia. It is best known for being the location of the Warragamba Dam and Lake Burragorang, which form a major part of the water supply to the Sydney region.Prior to the creation of...
and Coxs River before these rivers were dammed.
Habitat
In the freshwater reaches of coastal rivers in the warmer months, Australian bass require reasonable quality, unsilted habitats with adequate native riparian vegetation and in-stream cover/habitat. Australian bass generally sit in cover during the day. However, they are fairly flexible about the type of cover used. Sunken timber (“snags”), undercut banks, boulders, shade under trees and bushes overhanging the water and thick weedbeds are all used as cover. Such cover does not need to be in deep water to be used; Australian bass are happy to use cover in water as shallow as 1 metre in depth.Australian bass are strong swimmers at all sizes and can easily traverse rapids and fast-flowing water. However, they generally avoid sitting directly in currents to conserve energy.
At night Australian bass display pelagic (“near-surface”) behaviour and actively hunt prey in shallow water and at the water's surface.
When aggregated for spawning in the broad reaches of estuaries in winter, Australian bass are less cover oriented, and generally sit in deeper water.
Diet
Common items in the diet of Australian bass are:- terrestrial insectInsectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, particularly cicadaCicadaA cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
s - aquatic macroinvertebrates, particularly TrichopteraTrichopteraThe caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
larvae - crustaceans in the forms of freshwater shrimpShrimpShrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s and estuarine prawnPrawnPrawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
s - small fish, particularly flathead gudgeon (Philhypnodon grandiceps), which are common in their freshwater habitats.
However, Australian bass are fierce predators and any small creature that swims across a bass pool such as (introduced) mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
and native lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s or frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s are at risk of being taken by a large Australian bass, and are regularly taken.
Growth and age
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 occur every one or two decades. Maximum age recorded so far is 22 years.As with other Macquaria
Macquaria
The Macquaria genus is a genus of medium-sized, predatory native fish in the Percichthyidae family. The Macquaria genus was created by merging the old genera Plectrotripes and Macquaria and Percalates...
species, there is sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in Australian bass. Males tend to 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. Males reach sexual maturity at around 3–4 years of age, females at 5–6 years of age.
Reproduction
Australian bass spawn in estuariesEstuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
in winter, generally in the months of July or August.
The salinity range in which Australian bass spawn is still not clear. Estuaries are dynamic habitats with daily fluxes in salinity due to tides, and are also affected by droughts, floods and freshes (minor, temporary rises in flow), making measurements of preferred spawning salinities for wild Australian bass difficult.
Australian bass spawn in salinities of 8–12 parts per thousand (salt water is approximately 36 ppt), based on capture of recently spawned larval and juvenile Australian bass in estuaries. Australian bass sperm have no viability at or below 6 ppt, but are most viable at 12 ppt, the latter probably being the most relevant fact. However, it has been reported that Australian bass spawned in salinities of 12–18 ppt, with this statement based on fishermens' reports of observing wild Australian bass spawnings and some unpublished data gathered by the NSW Fisheries Department.
Artificial breeding of Australian bass is carried out at much higher salinities than natural.
Australian bass are highly fecund, with a reported mean fecundity ("fertility") of 440,000 eggs from the mature wild female specimens examined, and one very large specimen yielding 1,400,000 eggs. The eggs are reported as being demersal ("sinking") in natural spawning salinities, in which case estuarine vegetation such as sea grass almost certainly play an important role in "trapping" and protecting eggs. Larvae hatch in 2–3 days. Juvenile Australian bass migrate into the freshwater reaches after spending several months in estuarine waters.
Despite spawning in estuaries, Australian bass rely on floods coming down river systems into the estuaries throughout the winter period, both to stimulate migration and spawning in adult Australian bass and for strong survival and recruitment of Australian bass larvae.
Australian bass adults and larvae may also enter the sea (the latter perhaps involuntarily) during winter spawning in times of flood. It has been reported:
The presence of field-caught larvae of both species on incoming tides in Swansea Channel indicates that the larvae have spent some time in the ocean... Macquaria novemaculeata adults move downstream into estuaries to spawn in water of suitable salinity. In low rainfall years, the spawning location is further upstream than in wet years, when spawning can occur in shallow coastal waters adjacent to estuaries (Searle, pers. comm.). Mature M. novemaculeata adults can be found outside of estuaries in wet years (Williams, 1970). This is verified by the collection of mature adults by trawl in July 1995 in 11–17 m of water off Newcastle, NSW (AMS I.37358-001).
This kind of movement leads to some genetic interchange between river systems and is important in maintaining a high degree of genetic homogeneity ("sameness") in Australian bass stocks and preventing speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
. However, this movement has not prevented distinct genetic profiles and subtle morphological ("body shape") differences developing in different river systems. These findings indicate it is important to use the appropriate regional Australian bass stocks for artificial breeding and stocking projects.
Conservation
Wild Australian bass stocks have declined seriously since European settlement.Dams and weirs blocking migration of Australian bass both to estuaries and to the upper freshwater reaches of coastal rivers is the most potent cause of decline. Most coastal rivers now have dams and weirs on them. If Australian 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 Australian bass from the vast majority of their habitat. It is estimated for example that Tallowa Dam on the Shoalhaven River
Shoalhaven River
The Shoalhaven River is a river rising from the Southern Tablelands and flowing into the ocean near Nowra on the South Coast of New South Wales, Australia.- History :...
, once an Australian bass stronghold, currently excludes wild Australian bass from more than 80% of their former habitat (in early 2010 however a "fish lift" was fitted to the dam). Dams and weirs also diminish or completely remove flood events required for effective breeding of adult bass and effective recruitment of juvenile Australian bass. A related issue is the myriad of other structures on coastal rivers such as poorly designed road crossings that (often needlessly) block migration of Australian bass.
Another potent cause of decline is habitat degradation. Unfortunately poor land management practices have been the norm historically in Australia. Complete clearing of riparian (river bank) vegetation, stock trampling river banks, and massive siltation from these poor practices as well as poor practices in the catchment, can severely degrade and silt coastal rivers to the point of being uninhabitable for Australian bass. The Bega River
Bega River (New South Wales)
The Bega River is located in the far South Coast of New South Wales, Australia. The river rises in the Kybeyan Range, part of the Great Dividing Range, and discharges into the South Pacific Ocean at the town of Tathra. The river is known as the Bemboka River in its upper reaches and its major...
in southern New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
is a particularly salutory example of a coastal river so stripped of riparian vegetation and so silted with coarse granitic sands from poor land management practices, that the majority of it is now completely uninhabitable by Australian bass and other native fish.
As a slow-growing fish, Australian bass are vulnerable to overfishing, and overfishing has been a driver of decline in Australian bass stocks in past decades. However, the situation has improved markedly now the majority of fishermen are practicing catch and release
Catch and release
Catch and release is a practice within recreational fishing intended as a technique of conservation. After capture, the fish are unhooked and returned to the water before experiencing serious exhaustion or injury...
with Australian bass.
Hatchery breeding and stocking of Australian 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. Stockings can also mask and divert attention away from serious habitat degradation and decline of wild stocks in catchments.
Fishing
Fishing for Australian bass is 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, extraordinarily fast and powerful for their size. Their extraordinary speed and power is probably due to their significant, strenuous annual migrations for spawning and a life-style that is migratory in general. Australian bass in their natural river habitats are not to be underestimated; they head straight for the nearest snagSnag
In forest ecology, a snag refers to a standing, partly or completely dead tree, often missing a top or most of the smaller branches. In freshwater ecology it refers to trees, branches, and other pieces of naturally occurring wood found sunken in rivers and streams; it is also known as coarse woody...
s (sunken timber) when hooked and light but powerful tackle and stiff drag settings are needed to stop them.
As mentioned above, during the day Australian bass generally remain close to or in cover (e.g. snags, overhanging trees), and small plug lures and flies
Artificial fly
An artificial fly or fly lure is a type of fishing lure, usually used in the sport of fly fishing . In general, artificial flies are the bait which fly fishers present to their target species of fish while fly fishing...
cast close to such cover are used. In recent years fly fishing
Fly fishing
Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...
for Australian bass using surface flies imitating cicadas has proven to be extremely effective. At night Australian bass are a roaming pelagic feeder and surface lure
Surface lure
A surface lure is a fishing lure designed to waddle, pop, lock, drop, pulse, twitch or fizz across the surface of the water as it is retrieved, and in doing so imitate surface prey for fish such as mice, lizards, frogs, cicadas, moths and small injured fish....
s (which waddle or fizz across the surface of the water) are used. The large and sudden explosion a good Australian 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 still a highly migratory when in the freshwater reaches of rivers, and can also be an extremely wary fish in these habitats, much more so than exotic trout species.
Australian bass fishermen almost exclusively practice catch and release
Catch and release
Catch and release is a practice within recreational fishing intended as a technique of conservation. After capture, the fish are unhooked and returned to the water before experiencing serious exhaustion or injury...
, which is necessary for the preservation of wild Australian 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 Australian bass hit lures with great ferocity and are consequently almost impossible to unhook on barbed hooks. Conversely, Australian bass are swiftly and easily released if barbless hooks are used.
Responsible fishermen now avoid fishing for wild Australian bass in estuaries in winter, so that this increasingly pressured native fish can spawn in peace. In late July 2007 the NSW Fisheries Department announced a new closed season for Australian bass and estuary perch, from 1 June to 31 August.