The river blackfish (''Gadopsis marmoratus'') is a freshwater fish endemic to the temperate waters of south-eastern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is found from southern

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

through to central

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

, including in the

Murray Murray may refer to: Businesses * Murray (bicycle company), an American manufacturer of low-cost bicycles * Murrays, an Australian bus company * Murray International Trust, a Scottish investment trust * D. & W. Murray Limited, an Australian who ...

- Darling river system. It is also found in some eastern and southern flowing coastal rivers. Found primarily in upland and "midland" habitats, though early records of fish fauna suggest it was originally far more extensively distributed and was found in some

lowland Upland and lowland are conditional descriptions of a plain based on elevation above sea level. In studies of the ecology of freshwater rivers, habitats are classified as upland or lowland. Definitions Upland and lowland are portions of ...

habitats as well. Originally, river blackfish co-inhabited many of its lowland and "midland" habitats with species such as Murray cod and

golden perch The golden perch (''Macquaria ambigua'') is a medium-sized, yellow or gold-coloured species of Australian freshwater fish found primarily in the Murray-Darling River system, though a subspecies is found in the Lake Eyre-Cooper Creek system, an ...

, and its upland habitats with species such as

trout cod The trout cod (''Maccullochella macquariensis'') or bluenose cod, is a large predatory freshwater fish of the genus ''Maccullochella'' and the family Percichthyidae, closely related to the Murray cod. It was originally widespread in the south ...

and

Macquarie perch The Macquarie perch (''Macquaria australasica'') is an Australian native freshwater fish of the Murray-Darling river system. It is a member of the family Percichthyidae and is closely related to the golden perch (''Macquaria ambigua''). The ...

. It is a popular angling fish in some parts of its range.

Description

River blackfish are elongated with a rounded body, distinct snout and large mouth, and small to moderate sized eyes. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

, soft

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

and

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

are rounded. The spiny dorsal fin is low, weak and blends into the soft dorsal fin. Colour varies but is usually either yellow or green with dark green mottling, or a very dark purple/black colour. It is an ambush predator that takes

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

, small fish and aquatic insects. It is strongly nocturnal. Murray-Darling river blackfish show a maximum size of around 30 cm and < 0.8 kg, with larger specimens from coastal drainages reaching up to 60 cm (Gellibrand River). It is a highly underrated sportsfish, particularly the Southern form (see below). It is fast and strong, and has been shown to take

flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

and lures, even surface lures, in addition to the more usual worm baits. There is an unofficial world record caught by Piotr Pomorski on a WildBait Lure, in Victoria Australia that measured 70 cm in length.

Range and classification

Endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to south-eastern

, river blackfish like many Murray-Darling native fishes have managed to cross the

Great Dividing Range The Great Dividing Range, also known as the East Australian Cordillera or the Eastern Highlands, is a cordillera system in eastern Australia consisting of an expansive collection of mountain ranges, plateaus and rolling hills, that runs rough ...

via natural river capture events and so are found in south-flowing coastal rivers and streams in the eastern half of

. These fish are now often referred to as southern river blackfish. This population shows a far great maximum size of 60 cm or more and about . Specimens this large were likely to be very old — 30 years or more — and are rarely seen now. Southern river blackfish may be a separate species. The taxonomy does not yet reflect to this. River blackfish continue the trend present in Murray-Darling native fish of speciating into primarily

species and upland species, with the upland species being in this case the

two-spined blackfish The two-spined blackfish (''Gadopsis bispinosus'') is a species of temperate perch endemic to Australia. It is found in the cool, clear, strong-flowing, cobble bottomed, sub-alpine rivers and streams (ranging from small to large) in the southe ...

, ''Gadopsis bispinosus''. The two-spined blackfish is a more specialised upland inhabitant, and is found in the strongly flowing, cobble-bottomed sub-alpine rivers and streams of northeast

, southeast

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, and the

Australian Capital Territory The Australian Capital Territory (commonly abbreviated as ACT), known as the Federal Capital Territory (FCT) until 1938, is a landlocked federal territory of Australia containing the national capital Canberra and some surrounding townships. ...

. While the split may be between lowland (or midland) and upland, there are overlaps in their range, and river blackfish are found in many upland habitats. There are also indications river blackfish populations in the southern and northern halves of the Murray-Darling river system may represent two distinct species or sub-species, with genetic and other differences. The ''

Gadopsis ''Gadopsis'' is a genus of temperate perches endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to ...

'' blackfish and the ''

Maccullochella ''Maccullochella'' is a genus of large Australian predatory freshwater fish within the family Percichthyidae. The genus ''Maccullochella'' was named after an early Australian fish researcher with the surname ''McCulloch''. The ''Maccullochella'' ...

'' cods (such as the Murray cod, ''Maccullochella peelii'') are strongly similar. There are some grounds for believing blackfish may be a smaller version of Murray cod, inhabiting similar niches but in habitats are too small for Murray cod (having said this, their distributions originally overlapped substantially), and there are grounds for believing that blackfish and Murray cod have drawn heavily on common genes at the family level.

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

, for instance, has scrapped the family Gadopsidae and listed the blackfishes as members of the temperate perch family, ''

Percichthyidae The members of the family Percichthyidae are known as the temperate perches. They belong to the order Perciformes, the perch-like fishes. The name Percichthyidae derives from the Latin ''perca'' for perch and Ancient Greek ἰχθύς, ''ichthy ...

''. A

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

study has confirmed a relationship between the Blackfish and the Percichthyidae but the exact relationship was not resolved in that study. Further study is needed to resolve the relationship between the blackfish and the ''Percichthyidae''. In addition, molecular studies have supported the view that ''G. marmoratus'' is a

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

of five different species, these include a species in the Murray-Darling Basin and four species in coastal freshwaters. One of these forms from Victoria has been named as ''Gadopsis gracilis''. Blackfish have a recruitment method similar to Murray cod, but with more specialisation to upland habitats. Blackfish spawn in spring and lay a very limited number of large, adhesive eggs (<1000) on sunken timber (

snags In forest ecology, a snag refers to a standing, dead or dying 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 ...

), or in the case of two-spined blackfish on submerged rocks. Similar to Murray cod, the male guards the eggs until they hatch. Upon hatching the larval blackfish are, uniquely, attached to their ruptured egg case by a tether until the yolk sac is largely used and the larvae are ready to commence exogenous feeding. (This unique structure is presumably an adaptation to upland river/stream habitats, to prevent larvae being swept away in currents.)

Conservation

Blackfish have declined very seriously due to

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

, stream

siltation Siltation, is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or ...

and snag removal, and predation and competition by

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

, particularly introduced trout species. Recent bushfires in south-eastern Australia (2003–2006) have filled many blackfish rivers with large quantities of silt, and infilled the interstices ("gaps") between larger rocks that blackfish normally use as a refuge from predatory alien trout species. The presumed result will be increased levels of alien trout predation on blackfish, and the long-term future of blackfish species is now of some concern. The blackfish species are very low in fecundity, slow-growing and long-lived, and have low migratory tendencies, so are extremely vulnerable to overfishing and localised extinctions. River Blackfish are a protected species in South Australia.

References

* * * Jackson, P. D. (1978). "Spawning and early development of the River Blackfish", ''Gadopsis marmoratus'' Richardson (Gadopsiformes: Gadopsidae) in the McKenzie River, Victoria. ''Australian Journal of Marine and Freshwater Research'' 29: 293–298. * Jerry, D.R., Elphinstone, M.S and Baverstock, P.R. (2001). "Phylogenetic Relationships of Australian Members of the Family Percichthyidae Inferred from Mitochondrial 12S rRNA Sequence Data". ''Molecular Phylogenetics and Evolution'' 18: 335–347.

External links

Native Fish Australia – River Blackfish page
{{Taxonbar, from=Q3094241

river blackfish The river blackfish (''Gadopsis marmoratus'') is a freshwater fish endemic to the temperate waters of south-eastern Australia. It is found from southern Queensland through to central Victoria, including in the Murray- Darling river system. It ...

Taxa named by John Richardson (naturalist) Freshwater fish of Australia