The Australian bass (Percalates novemaculeatus) and an extremely popular game fish species among anglers. The species was simply called perch in most coastal rivers where it was caught until the 1960s, when the name "Australian bass" started to gain popularity.

In the 1970s Australian bass and estuary perch were moved into the genus Macquaria – one of a number of Australian genera in the family Percichthyidae – along with two species of native perch from the Murray-Darling Basin, golden perch (Macquaria ambigua) and Macquarie perch (Macquaria australasica). Prior to that, Australian bass and estuary perch were in a separate genus, Percalates. (The generic name Percalates is a compound of the generic names Perca and Lates, and arose from an early, erroneous taxonomic belief that Australian bass were an old world perch related to barramundi (Lates calcarifer)).

Results from research using genetic MtDNA analysis revealed that Australian bass and estuary perch are not closely related to golden perch and Macquarie perch, which resulted in researchers resurrecting the genus Percalates and referring to Australian bass and estuary perch as Percalates novemaculeatus and Percalates colonorum respectively. Unexpectedly Percalates was found to be genetically closer to the genus Maccullochella (Murray cod and other cod species) than to the remnant genus Macquaria (golden perch and Macquarie perch). However, more recent studies have found Percalates to be the earliest-diverging genus within the order Centrarchiformes, being only distantly related to Macquaria and other percichthyids, and have been placed in their own putative family Percalatidae.

Steindachner does not explicitly state the reasons behind the surprisingly ambiguous specific name novemaculeata that he created for Australian bass. There are several possibilities. It may be a Latin rendering of "new" (novem) and "spotted" (maculeata) and refer to the distinct black blotches juvenile bass are temporarily marked with when very small (i.e. <). It may be a Latin rendering of "in an unusual manner" (nove) and "spotted" (maculeata) and refer to the specimens he examined being "spotted":

The most likely explanation however is a Latin rendering of "nine" (novem) and "spines/needles" (aculeata) and refer to the spiny dorsal fin, which is relatively high and sharp and which Steindachner indicates is usually (but not always) composed of nine dorsal spines:

thumb|right|An Australian bass (summer, freshwater reaches) before release.

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 fins. Their spiny dorsal fin is relatively high, 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 metallic 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. Wild river fish average around and . A river fish of or larger is a good specimen. Maximum size in rivers appears to be around and in southern waters, and around and in northern waters. Australian bass stocked in man-made impoundments (where they cannot breed) grow to greater average and maximum weights than this.

Range

Australian bass are found in coastal rivers and streams from Wilsons 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 not found in the Murray-Darling system. Although the system is extensive, it terminates in a sequence of coastal lakes and lagoons and has only one shallow and changeable entrance to the Southern Ocean — features that appear 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 in the estuarine reaches in winter, and are highly migratory in general.

A general description of the typical migratory pattern for adult Australian bass in the central (NSW) portion of their range 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 from the north to the south of their range, with bass in the far south of their range appearing to move and recruit in spring rather than winter, probably because of colder water temperatures. Males inhabit the lower freshwater reaches of rivers while females travel far into the middle and even upper freshwater (upland) reaches. The distance Australia bass travel upstream appears to be limited only by flows and impassable barriers (historically, waterfalls; today, often, dams). Thus, historically, the effective altitudinal limit for Australian bass has been as high as in some river systems. For instance, Australian bass originally migrated up to the Dalgety region in the Snowy River, well above Oallen Crossing on the Shoalhaven River (including the lower reaches of tributary Mongarlowe River) and far up the Warragamba River 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.

thumb|Australian bass easily traverse rapids like these in their coastal river habitats. However, they require floods or freshes to drown out more significant rapids and cascades and make them passable.

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 insects, particularly cicadas
  • aquatic macroinvertebrates, particularly Trichoptera (caddisfly) larvae
  • crustaceans in the forms of freshwater shrimps and estuarine prawns
  • small fish, particularly flathead gudgeon (Philhypnodon grandiceps), which are common in their freshwater habitats. 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. For many years, the maximum age recorded in wild Australian bass was 22 years. However, a wild bass from the Genoa River system has now been aged at 47 years of age. The same study recorded numerous wild bass aged 19 years of age and 29 years of age (corresponding to two separate years of strong recruitment). There is uncertainty about the salinity levels that Australian bass spawn in. 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. However, based on capture of recently spawned larval and juvenile Australian bass in estuaries, the species appears to spawn in a salinity range of 8–12 parts per thousand (salt water is approximately 36 ppt).

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.</blockquote>

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, along with research showing significant differences in seasonal timing of spawning and migration in far south populations

Citations

Additional references

  • Kaminskas S (2024). Migratory Flows and Stochastic Blows: A study of Australian grayling (Prototroctes maraena) and other native fish species of the Deua River, New South Wales, Australia. Published by the author, Canberra, Australia. http://dx.doi.org/10.13140/RG.2.2.24039.05283
  • Mallen-Cooper M (1992). Swimming ability of juvenile Australian bass, Macquaria novemaculeata (Steindachner), and juvenile barramundi, Lates calcarifer (Bloch), in an experimental vertical-slot fishway. Australian Journal of Marine and Freshwater Research 43: 823–833.
  • Steindachner F. (1866:50). Anzeiger der Kaiserlichen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftlichen Classe v. 3 (no. 7); Steindachner Abstract Port Jackson, New South Wales, Australia. Syntypes: (4) NMW 38828 (2). Appeared first in the abstract as above, then in Steindachner (1866:428) [p.&nbsp;5 of separate], Pl. 2 (fig. 1) Steindachner Full Description (In German).
  • Underwater Video of wild Australian Bass on Youtube
  • Native Fish Australia – Australian bass page.
  • Includes information about growing out Australian Bass
  • Fishes of Australia : Macquaria novemaculeata