River Blackfish
Encyclopedia
The river blackfish, is an Australia
n native freshwater fish of the Murray
-Darling
river system, found from southern Queensland
through to central Victoria
. 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 habitats as well. Originally, river blackfish co-inhabited many of its lowland and "midland" habitats with species such as Murray cod
and golden perch
, and its upland habitats with species such as trout cod
and Macquarie perch
.
and anal fin 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 a carnivore that takes crayfish
, shrimp
, the occasional small fish and occasional surface prey. It is strongly nocturnal.
Murray-Darling river blackfish show a maximum size of around 30 cm and < 0.8 kg
.
It is a highly underrated sportsfish, particularly the Southern form (see below). It is fast and strong, and has been shown to take flies
and lures, even surface lures, in addition to the more usual worm baits.
to south-eastern Australia
, river blackfish like many Murray-Darling native fishes have managed to cross the Great Dividing Range
via natural river capture events and so are found in south-flowing coastal rivers and streams in the eastern half of Victoria
. 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 5.5 kg. Specimens this large were likely to be very old — 30 years or more — and are rarely seen now. Logic suggests that due to these dramatic size differences, as well as isolation from the parent Murray-Darling species, genetic drift and natural selection, southern river blackfish are separate species. The taxonomy has not been reflected to update this.
River blackfish continue the trend present in Murray-Darling native fish of speciating into primarily lowland species and upland species, with the upland species being in this case the two-spined blackfish
, 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 Victoria
, southeast New South Wales
, and the Australian Capital Territory
. Though with the blackfish species perhaps you would say the split is lowland/midland and upland as there are overlaps in their range, and river blackfish are found in many upland habitats.
There are also indications that 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 similarities between the Gadopsis
blackfish and the Maccullochella
cods (such as the Murray cod
, Maccullochella peelii) are striking. There are some grounds for believing that Blackfish may be in effect a smaller version of Murray cod, inhabiting similar niches to Murray cod but in habitats that 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
, for instance, has scrapped the family Gadopsidae and listed the blackfishes as members of the temperate perch family, Percichthyidae. A mitochondrial DNA
study has confirmed a relationship between the Blackfish and the Percichthyidae but the exact relationship was not resolved in that study (Jerry et al., 2001). Further study is needed to resolve the relationship between the blackfish and the Percichthyidae.
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), 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.)
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...
n native freshwater fish of the Murray
Murray River
The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
-Darling
Darling River
The Darling River is the third longest river in Australia, measuring from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales. Including its longest contiguous tributaries it is long, making it the longest river system in Australia.The...
river system, found from southern 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...
through to central 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....
. 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 habitats as well. Originally, river blackfish co-inhabited many of its lowland and "midland" habitats with species such as 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 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....
, and its upland habitats with species such as trout cod
Trout Cod
The trout cod or bluenose cod, Maccullochella macquariensis, is a large predatory freshwater fish of the Maccullochella genus and the Percichthyidae family which was originally found in the south-east corner of the Murray-Darling river system in Australia...
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 ....
.
Description
River blackfish are elongated with a rounded body, distinct snout and large mouth, and small to moderate sized eyes. The caudal fin, 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...
and anal fin 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 a carnivore that takes crayfish
Crayfish
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...
, shrimp
Shrimp
Shrimp 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...
, the occasional small fish and occasional surface prey. It is strongly nocturnal.
Murray-Darling river blackfish show a maximum size of around 30 cm and < 0.8 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
.
It is a highly underrated sportsfish, particularly the Southern form (see below). It is fast and strong, and has been shown to take 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...
and lures, even surface lures, in addition to the more usual worm baits.
Range and classification
EndemicEndemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to south-eastern 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...
, river blackfish like many Murray-Darling native fishes have managed to cross the Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...
via natural river capture events and so are found in south-flowing coastal rivers and streams in the eastern half of 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....
. 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 5.5 kg. Specimens this large were likely to be very old — 30 years or more — and are rarely seen now. Logic suggests that due to these dramatic size differences, as well as isolation from the parent Murray-Darling species, genetic drift and natural selection, southern river blackfish are separate species. The taxonomy has not been reflected to update this.
River blackfish continue the trend present in Murray-Darling native fish of speciating into primarily lowland species and upland species, with the upland species being in this case the two-spined blackfish
Two-spined blackfish
The two-spined blackfish, Gadopsis bispinosus, is an Australian native freshwater fish. It is a speciated, more specialised upland variant of the river blackfish, Gadopsis marmoratus....
, 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 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....
, southeast 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...
, and the Australian Capital Territory
Australian Capital Territory
The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory...
. Though with the blackfish species perhaps you would say the split is lowland/midland and upland as there are overlaps in their range, and river blackfish are found in many upland habitats.
There are also indications that 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 similarities between the Gadopsis
Gadopsis
The Gadopsis genus is a genus of small to medium sized predatory Australian native freshwater fish. The Gadopsis genus was formerly considered to be in a family of its own but is now generally considered to be part of the Percichthyidae family...
blackfish and 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....
cods (such as the 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...
, Maccullochella peelii) are striking. There are some grounds for believing that Blackfish may be in effect a smaller version of Murray cod, inhabiting similar niches to Murray cod but in habitats that 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
FishBase is a comprehensive database of information about fish species . 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. A mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
study has confirmed a relationship between the Blackfish and the Percichthyidae but the exact relationship was not resolved in that study (Jerry et al., 2001). Further study is needed to resolve the relationship between the blackfish and the Percichthyidae.
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), or in the case of two-spined blackfish
Two-spined blackfish
The two-spined blackfish, Gadopsis bispinosus, is an Australian native freshwater fish. It is a speciated, more specialised upland variant of the river blackfish, Gadopsis marmoratus....
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.)