Eastern freshwater cod
Encyclopedia
Eastern freshwater cod, Maccullochella ikei, also known as eastern cod, are a large and striking predatory freshwater fish of the Maccullochella
genus and the Percichthyidae family, that occur in the coastal Clarence River system of north-eastern New South Wales
. Eastern freshwater cod are closely related to the Murray cod
of the Murray-Darling river system, and are considered an icon of the Clarence River system.
A long-lived, slow-growing species, eastern freshwater cod are gravely threatened by poaching, habitat degradation and catastrophic natural events such as bushfires. Eastern freshwater cod are now protected by law.
in northern New South Wales
, Australia
. The Clarence River system is an extensive East Coast drainage with many tributaries of differing size. By Australian standards the Clarence River and its major tributaries the Mann and Nymboida Rivers are extremely large rivers with extremely large flow volumes. Eastern freshwater cod originally occurred in great abundance through all of the system, to significant altitudes, though reportedly were never found above the large falls many tributaries feature in their upper reaches.
The indigenous cod population of the Richmond River system (Richmond River Cod
), now extinct, are believed to have been a population of eastern freshwater cod. The Richmond River has been restocked with fingerlings produced from Clarence River cod but there is no evidence that they are breeding (Anon, 2004).
In eastern freshwater cod the spiny dorsal fin is moderate in height and is partially separated by a notch from the high, rounded soft dorsal fin. Soft dorsal, anal and caudal (tail) fins are all large and rounded, and are dusky grey or black with distinct white edges. The large, rounded pectoral fins are usually similar in colour to flanks. The pelvic fins are large and angular, set forward of the pectoral fins, and are usually a translucent greyish-white colour, tending toward opacity in large fish. The leading greyish-white coloured rays on the pelvic fins split into two trailing filaments. These filaments are significantly longer than in Murray cod.
Eastern freshwater cod are vary from cream or greyish-white to yellow on their ventral (“belly”) surface. Their back and flanks are usually an intense yellow or gold in colour, overlain with a dense pattern of black to very dark green mottling. The effect is a marbled appearance sometimes reminiscent of a leopard's markings. Colouration does vary considerably however and eastern freshwater cod from dark, heavily shaded habitats can be very dark or almost black in colour.
, Maccullochella peelii, that are present in tributaries of the Murray-Darling Basin
on the western side of the Great Dividing Range
. Murray cod entered an east coast river system, likely the Clarence, via a natural event somewhere between 0.62 and 1.62 million years ago (mean estimate 1.1 million years ago), as estimated by DNA
divergence rates. Subsequent isolation from Murray cod
populations, the founder effect
, genetic drift
and natural selection
all led eastern freshwater cod to diverge from and become a separate species to Murray cod
(Nock et al., 2010). (See allopatric speciation
.)
In addition to eastern freshwater cod of the Clarence River system, there are/were cod in several other coastal river systems. In total, at the time of European settlement of the Australia in the 18th century, naturally occurring cod were present and extremely abundant in four East Coast river systems:
Several genetic studies have found that eastern freshwater cod, in the southern-most of these four rivers, and Mary River cod, in the northern-most of these four rivers, are more closely related to each other than to Murray cod (Jerry et al., 2001; Bearlin & Tikel, 2002; Nock et al., 2010). This suggests that Murray cod only managed to cross into east coast river systems once. It is not clear which of the four river systems was the original entry point. Geomorphological evidence meant the Clarence River was long suspected as the entry point but latest genetic evidence (Nock et al., 2010) suggests the Mary River system could also have been the original entry point. It is worth noting that dramatic drops in sea-level during glacial periods (aka "Ice Ages") and/or "lateral" river capture events could easily have seen these four coastal river systems linked at times and freshwater cod gaining access to each one. The mean estimate for genetic separation of Mary River cod and Eastern Freshwater Cod is only 300,000 years (Nock et al., 2010).
DNA analysis reveals eastern freshwater cod of the Clarence River system went through a calamitous bottleneck a couple of thousand years ago, in which the majority of the population perished. This was likely due to a sequence of catastrophic drought, whole-of-catchment scale bushfires and widespread ash-induced fish kill
s. Eastern freshwater cod recovered from this event and were in abundance by the time of European settlement, but appear to have lost much of their genetic diversity in this event. (The genetic diversity of eastern freshwater cod has been further reduced by catastrophic declines caused by European settlers and the stocking of hatchery fish with poor genetic diversity.)
and aggressive. The bulk of their diet is based on crustacean
s (the large, clawed Macrobrachium shrimp and the small, clawless Paratya shrimp) and other fish, but they are powerful opportunistic predators and are also known to take insects (e.g. cicadas), frog
s, snake
s, lizards, birds and small mammals.
. The oldest eastern freshwater cod yet aged is only 14 years of age, but this reflects limited sampling and many decades of overfishing and poaching, that have led to the loss of most large individuals (Butler & Rowland, 2008). There is little doubt the species has the potential to reach or even exceed the maximum age recorded in Murray cod
(48 years).
Eastern freshwater cod are sexually mature at 4 or 5 years old, and at sizes as small as 700 g, the latter being markedly different to Murray cod
(Butler & Rowland, 2008, 2009). This far smaller size at sexual maturity is likely an evolved adaptation to the rocky, low-nutrient and often quite small waterways eastern freshwater cod are found in. The trout cod
, a Maccullochella
cod also once found in small, rocky, low-nutrient streams in the upland reaches of the Murray-Darling system, displays a similar trait, also reaching sexual maturity at a far smaller size than Murray cod
. Eastern freshwater cod spawn in early spring when water temperatures reach 16°C, using rock structures as sites for the adhesive eggs. Most other aspects of their spawning, including the guarding of eggs and newly hatched larvae by the male fish, are similar to Murray cod
(Butler & Rowland, 2009). However, there are some indications that in contrast to Murray cod larvae, eastern freshwater cod larvae may not drift in river currents for several days after leaving their nest. This would be a notable difference in the larval ecology between the two species, however more research is required to confirm this.
It is important for anglers to avoid any accidental captures of eastern freshwater cod in winter when they are developing their roe, or in early spring when spawning is occurring, as research indicates this results in resorbed roe or abandoned nests respectively and a failed spawning effort (Butler & Rowland, 2009). There is now a total fishing closure on the Mann and Nymboida Rivers and their tributaries between 1 August to 31 October (inclusive) each year specifically to protect the eastern freshwater cod from accidental capture during their breeding season (NSW DPI, 2008).
It should be noted that anglers are not allowed to deliberately target eastern freshwater cod.
A number of factors have led to the endangerment of eastern freshwater cod. One factor is gross overfishing, including with lines, nets, explosives and spears. As a very slow growing, top predator with low fecundity ("fertility") eastern freshwater cod are even more vulnerable to overfishing than their relative Murray cod
. Another factor was severe whole-of-catchment scale bushfires in the 1930s which caused very large, widespread ash-induced fish kills. Gross habitat degradation and siltation by poor farming practices (such as clearing riverbank vegetation and allowing stock to trample river banks) is another factor that has destroyed many eastern freshwater cod habitats, and unfortunately some of these poor farming practices continue unchecked today. Finally, serious cyanide pollution from mining caused serious fish kills in the late 19th century/early 20th century (Anon, 2004).
All of these factors have reduced the once abundant eastern freshwater cod to an endangered species with a limited distribution in the Clarence River System.
The same factors have led to the extinction of Richmond and Brisbane River cod and the endangerment of Mary River cod as well.
Eastern freshwater cod were recognised as a potentially separate and endangered species of cod in 1984, and were declared a protected species in that year. Subsequent research confirmed they are indeed a separate and endangered species of cod; they remain a protected species. Disturbing levels of illegal poaching are taking place however and are not being tackled.
A restocking programme was undertaken by the government of New South Wales
from 1984 to 1989. The government-run stocking programme was ill-advisedly closed after 1989 and contracted to a private operation, which produced and stocked fingerlings until the late 1990s. The eastern freshwater cod stocking programme was then suspended after genetic research indicated the fingerlings being produced had very low levels of genetic diversity.
No eastern freshwater cod are currently being bred or stocked.
The NSW fisheries department has allowed the private operation that produced eastern freshwater cod fingerlings to retain broodfish and produce captive-reared eastern freshwater cod for the table fish market.
Concern has been expressed over the future of all eastern freshwater cod stocks in the Clarence River system after the NSW Fisheries department allowed a stocking of Australian bass
fingerlings from a completely different bio-region to proceed (Rowland, 2001). The fingerlings were contaminated with and introduced the banded grunter, Amniataba percoides, to the lower reaches of the river. The banded grunter is an extremely aggressive small native fish species. It is feared banded grunter may yet invade the main freshwater reaches of the Clarence River system with devastating impacts on eastern freshwater cod.
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 and the Percichthyidae family, that occur in the coastal Clarence River system of north-eastern 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...
. Eastern freshwater cod are closely related to 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...
of the Murray-Darling river system, and are considered an icon of the Clarence River system.
A long-lived, slow-growing species, eastern freshwater cod are gravely threatened by poaching, habitat degradation and catastrophic natural events such as bushfires. Eastern freshwater cod are now protected by law.
Range
Eastern freshwater cod are native to the Clarence River systemClarence River (New South Wales)
The Clarence River is situated in northeastern New South Wales, Australia. The river originates on the watershed that marks the Queensland border. After flowing south and northeast for 394 km it then empties into the Pacific Ocean at Iluka/Yamba. On its journey it passes through the towns of...
in northern 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...
, 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...
. The Clarence River system is an extensive East Coast drainage with many tributaries of differing size. By Australian standards the Clarence River and its major tributaries the Mann and Nymboida Rivers are extremely large rivers with extremely large flow volumes. Eastern freshwater cod originally occurred in great abundance through all of the system, to significant altitudes, though reportedly were never found above the large falls many tributaries feature in their upper reaches.
The indigenous cod population of the Richmond River system (Richmond River Cod
Richmond River cod
The Richmond River cod was a form of Maccullochella cod, now believed to have been eastern freshwater cod, Maccullochella ikei, that occurred naturally in the Richmond River system, an east coast river system in north-east New South Wales, Australia....
), now extinct, are believed to have been a population of eastern freshwater cod. The Richmond River has been restocked with fingerlings produced from Clarence River cod but there is no evidence that they are breeding (Anon, 2004).
Appearance and size
Eastern freshwater cod have been recorded to 41 kg, but are more common at sizes less than 5 kg. Eastern freshwater cod are a small to medium sized groper-like fish with a deep, elongated body that is round in cross section. They have a broad, scooped head, and a large mouth lined with pads of very small needle-like teeth. The jaws are equal or the lower jaw protrudes slightly. Their eyes are slightly larger and more prominent than in Murray cod.In eastern freshwater cod the spiny dorsal fin is moderate in height and is partially separated by a notch from the high, rounded soft dorsal fin. Soft dorsal, anal and caudal (tail) fins are all large and rounded, and are dusky grey or black with distinct white edges. The large, rounded pectoral fins are usually similar in colour to flanks. The pelvic fins are large and angular, set forward of the pectoral fins, and are usually a translucent greyish-white colour, tending toward opacity in large fish. The leading greyish-white coloured rays on the pelvic fins split into two trailing filaments. These filaments are significantly longer than in Murray cod.
Eastern freshwater cod are vary from cream or greyish-white to yellow on their ventral (“belly”) surface. Their back and flanks are usually an intense yellow or gold in colour, overlain with a dense pattern of black to very dark green mottling. The effect is a marbled appearance sometimes reminiscent of a leopard's markings. Colouration does vary considerably however and eastern freshwater cod from dark, heavily shaded habitats can be very dark or almost black in colour.
Origins
Eastern freshwater cod are a separate species of cod that originated from the Murray codMurray 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, that are present in tributaries of the Murray-Darling Basin
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...
on the western side of 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...
. Murray cod entered an east coast river system, likely the Clarence, via a natural event somewhere between 0.62 and 1.62 million years ago (mean estimate 1.1 million years ago), as estimated by DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
divergence rates. Subsequent isolation from 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...
populations, the founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
, genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
and natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
all led eastern freshwater cod to diverge from and become a separate species to 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...
(Nock et al., 2010). (See allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
.)
In addition to eastern freshwater cod of the Clarence River system, there are/were cod in several other coastal river systems. In total, at the time of European settlement of the Australia in the 18th century, naturally occurring cod were present and extremely abundant in four East Coast river systems:
- Clarence River system, northern New South WalesNew South WalesNew 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...
(eastern freshwater cod, Maccullochella ikei) - Richmond River system, northern New South Wales (Richmond River codRichmond River codThe Richmond River cod was a form of Maccullochella cod, now believed to have been eastern freshwater cod, Maccullochella ikei, that occurred naturally in the Richmond River system, an east coast river system in north-east New South Wales, Australia....
, Maccullochella ikei) - Brisbane River system, southern QueenslandQueenslandQueensland 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...
(Brisbane River codBrisbane River codThe Brisbane River cod was a unique form of Maccullochella cod that occurred naturally in the Brisbane River system, an east coast river system in south east Queensland, Australia...
, Maccullochella sp.) - Mary River system, central Queensland (Mary River codMary River codMary River cod are a Maccullochella cod found in the coastal Mary River system of southern Queensland, Australia...
, Maccullochella mariensis)
Several genetic studies have found that eastern freshwater cod, in the southern-most of these four rivers, and Mary River cod, in the northern-most of these four rivers, are more closely related to each other than to Murray cod (Jerry et al., 2001; Bearlin & Tikel, 2002; Nock et al., 2010). This suggests that Murray cod only managed to cross into east coast river systems once. It is not clear which of the four river systems was the original entry point. Geomorphological evidence meant the Clarence River was long suspected as the entry point but latest genetic evidence (Nock et al., 2010) suggests the Mary River system could also have been the original entry point. It is worth noting that dramatic drops in sea-level during glacial periods (aka "Ice Ages") and/or "lateral" river capture events could easily have seen these four coastal river systems linked at times and freshwater cod gaining access to each one. The mean estimate for genetic separation of Mary River cod and Eastern Freshwater Cod is only 300,000 years (Nock et al., 2010).
DNA analysis reveals eastern freshwater cod of the Clarence River system went through a calamitous bottleneck a couple of thousand years ago, in which the majority of the population perished. This was likely due to a sequence of catastrophic drought, whole-of-catchment scale bushfires and widespread ash-induced fish kill
Fish kill
The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...
s. Eastern freshwater cod recovered from this event and were in abundance by the time of European settlement, but appear to have lost much of their genetic diversity in this event. (The genetic diversity of eastern freshwater cod has been further reduced by catastrophic declines caused by European settlers and the stocking of hatchery fish with poor genetic diversity.)
Habitat and Diet
Eastern freshwater cod are found in clear, flowing rivers and streams with rocky beds and deep holes within the Clarence River system, to significant altitudes. The size of the rivers and streams they inhabit range from very small to very large. Eastern freshwater cod are territorialTerritory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
and aggressive. The bulk of their diet is based on crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s (the large, clawed Macrobrachium shrimp and the small, clawless Paratya shrimp) and other fish, but they are powerful opportunistic predators and are also known to take insects (e.g. cicadas), 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, snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s, lizards, birds and small mammals.
Age, Growth and Spawning
Growth is highly variable in eastern freshwater cod but overall is slower than in Murray codMurray 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...
. The oldest eastern freshwater cod yet aged is only 14 years of age, but this reflects limited sampling and many decades of overfishing and poaching, that have led to the loss of most large individuals (Butler & Rowland, 2008). There is little doubt the species has the potential to reach or even exceed the maximum age recorded in 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...
(48 years).
Eastern freshwater cod are sexually mature at 4 or 5 years old, and at sizes as small as 700 g, the latter being markedly different to 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...
(Butler & Rowland, 2008, 2009). This far smaller size at sexual maturity is likely an evolved adaptation to the rocky, low-nutrient and often quite small waterways eastern freshwater cod are found in. The 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...
, a 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....
cod also once found in small, rocky, low-nutrient streams in the upland reaches of the Murray-Darling system, displays a similar trait, also reaching sexual maturity at a far smaller size than 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...
. Eastern freshwater cod spawn in early spring when water temperatures reach 16°C, using rock structures as sites for the adhesive eggs. Most other aspects of their spawning, including the guarding of eggs and newly hatched larvae by the male fish, are similar to 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...
(Butler & Rowland, 2009). However, there are some indications that in contrast to Murray cod larvae, eastern freshwater cod larvae may not drift in river currents for several days after leaving their nest. This would be a notable difference in the larval ecology between the two species, however more research is required to confirm this.
It is important for anglers to avoid any accidental captures of eastern freshwater cod in winter when they are developing their roe, or in early spring when spawning is occurring, as research indicates this results in resorbed roe or abandoned nests respectively and a failed spawning effort (Butler & Rowland, 2009). There is now a total fishing closure on the Mann and Nymboida Rivers and their tributaries between 1 August to 31 October (inclusive) each year specifically to protect the eastern freshwater cod from accidental capture during their breeding season (NSW DPI, 2008).
It should be noted that anglers are not allowed to deliberately target eastern freshwater cod.
Conservation
Early records reveal eastern freshwater cod were extremely abundant in the Clarence River system as the time of European settlement. These records reveal eastern freshwater cod were so abundant they were caught "on demand" for diners at a riverside hotel, and were sometimes used as pig feed, the latter being quite shocking treatment and waste of a strikingly beautiful and valuable fish.A number of factors have led to the endangerment of eastern freshwater cod. One factor is gross overfishing, including with lines, nets, explosives and spears. As a very slow growing, top predator with low fecundity ("fertility") eastern freshwater cod are even more vulnerable to overfishing than their relative 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...
. Another factor was severe whole-of-catchment scale bushfires in the 1930s which caused very large, widespread ash-induced fish kills. Gross habitat degradation and siltation by poor farming practices (such as clearing riverbank vegetation and allowing stock to trample river banks) is another factor that has destroyed many eastern freshwater cod habitats, and unfortunately some of these poor farming practices continue unchecked today. Finally, serious cyanide pollution from mining caused serious fish kills in the late 19th century/early 20th century (Anon, 2004).
All of these factors have reduced the once abundant eastern freshwater cod to an endangered species with a limited distribution in the Clarence River System.
The same factors have led to the extinction of Richmond and Brisbane River cod and the endangerment of Mary River cod as well.
Eastern freshwater cod were recognised as a potentially separate and endangered species of cod in 1984, and were declared a protected species in that year. Subsequent research confirmed they are indeed a separate and endangered species of cod; they remain a protected species. Disturbing levels of illegal poaching are taking place however and are not being tackled.
A restocking programme was undertaken by the government of 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...
from 1984 to 1989. The government-run stocking programme was ill-advisedly closed after 1989 and contracted to a private operation, which produced and stocked fingerlings until the late 1990s. The eastern freshwater cod stocking programme was then suspended after genetic research indicated the fingerlings being produced had very low levels of genetic diversity.
No eastern freshwater cod are currently being bred or stocked.
The NSW fisheries department has allowed the private operation that produced eastern freshwater cod fingerlings to retain broodfish and produce captive-reared eastern freshwater cod for the table fish market.
Concern has been expressed over the future of all eastern freshwater cod stocks in the Clarence River system after the NSW Fisheries department allowed a stocking of Australian bass
Australian bass
Australian bass are a small to medium sized, primarily freshwater 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...
fingerlings from a completely different bio-region to proceed (Rowland, 2001). The fingerlings were contaminated with and introduced the banded grunter, Amniataba percoides, to the lower reaches of the river. The banded grunter is an extremely aggressive small native fish species. It is feared banded grunter may yet invade the main freshwater reaches of the Clarence River system with devastating impacts on eastern freshwater cod.