The trout cod (''Maccullochella macquariensis'') or bluenose cod, is a large predatory freshwater fish of the genus ''

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' ...

'' and the 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 ...

, closely related to the Murray cod. It was originally widespread in the south-east corner of the Murray-Darling river system in

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

, but is now an endangered species. In the 19th and early 20th centuries, when trout cod were widely recognised as a separate species by commercial fishermen, recreational fishermen, riverside residents and fisheries scientists, they were generally known as bluenose cod or simply bluenose, particularly in

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 ...

. In some parts of

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 ...

however they were also known as trout cod, and this common name was adopted when the species status of the fish was finally confirmed by genetic studies in the early 1970s. This choice of official common name was perhaps unfortunate; it has been suggested that bluenose cod is a more appropriate name as the name trout cod causes confusion amongst the Australian public. (Trout cod are an Australian native freshwater fish; they are not a hybrid between Murray cod and introduced trout species.) Percichthyidae - Maccullochella macquariensis

Percichthyidae - Maccullochella macquariensis

Trout cod are a listed species on a number of different registers including Endangered under the New South Wales Fisheries Management Act 1994, the Australian Commonwealth's Environment Protection and Biodiversity Conservation Act 1999, the Australian Capital Territory's Nature Conservation Act 1980 and by the World Conservation Union (IUCN). They are also listed as Threatened under the Victorian Flora and Fauna Guarantee Act 1998. Fossils of genus ''Maccullochella'' can be found from

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

epoch (from about 23.03 to 5.332 million years ago) to recent age, while the species ''Maccullochella macquariensis'' is present from Lower

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58upland habitats. During the 19th and early 20th centuries trout cod were recognised by the scientific community as separate species, due to differing habitat preferences, morphological differences (especially the much smaller size at sexual maturity) and differing spawning times. It was really only post

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

— by which time trout cod had become very rare or even extinct in much of their original range — that the erroneous idea that they were really just anomalous Murray cod gained any currency.

Habitat

Although there is/was a very substantial overlap in range, trout cod are essentially a more specialised upland sister species to Murray cod. Therefore, the trout cod's main habitats were the larger upland rivers and creeks, which they usually co-inhabited with Macquarie perch and one or both of the

blackfish Blackfish is a common name for the following species of fish, dolphins, and whales: Fish * Alaska blackfish, (''Dallia pectoralis''), an Esocidae from Alaska, Siberia and the Bering Sea islands * Black fish (''Carassioides acuminatus'') a cyprin ...

species. Historical research is confirming a primarily upland distribution for trout cod; recent governmental literature lacking such historical research and suggesting trout cod are primarily a lowland fish species must be considered inaccurate. Division into specialist upland and ''primarily''

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 p ...

species is a relatively common phenomena in native fish genera of the Murray-Darling and East Coast systems with other notable pairs shown in the following table: Trout cod are often found close to cover and in faster currents and in cooler waters than Murray cod. Their diet is essentially the same as Murray cod with adjustment made for size, eating mainly other fishes,

freshwater mussels Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does includ ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s, aquatic

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

s, small

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

and water fowl. However, recent anecdotal evidence suggests terrestrial insects made up a significant proportion of the trout cod's diet in upland rivers and streams. In the surviving Murray River population trout cod tend to stick to areas of deep water near banks, around snags, rocks or other large structure. However, historical accounts of trout cod in upland river habitats stated that trout cod were often found in shallow riffles and runs. Generally speaking, radio-tracked trout cod in the surviving Murray River population have small home ranges and may be a species which does not move away from their original base, except during the breeding season when they follow a common trend in Murray-Darling fish of migrating upstream prior to spawning. It seems likely that trout cod follow a similar pattern to Murray cod and return post spawning to their original location.

Diet

Trout cod are carnivores and feed on other fish, crustaceans (such as crayfish, yabbies and freshwater shrimp) as well as aquatic and terrestrial insects. Larvae are

pelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that do live on or near the bottom, and reef fish that are associated with coral re ...

and eat zooplankton.

Reproduction

Trout cod reach sexual maturity at 3 to 5 years (which corresponds to about 35 cm in males and 43 cm in females). Trout cod reach sexual maturity at a smaller size than Murray cod, which is an adaptation to the rocky, low nutrient and often quite small upland habitats trout cod were found in. Spawning of trout cod has never been observed in the wild and is not well understood. It is believed to be essentially the same as Murray cod but occurs about three weeks earlier and at significantly lower temperatures in waters shared by the two species. Trout cod are believed to spawn at temperatures as low as 15 degrees in upland rivers, using rocks as a spawning substrate; these are also clear adaptations to cool, rocky upland river habitats. Significantly, and unlike Murray cod, trout cod will not breed in earthen dam brood ponds; another indication that trout cod are a more specialised upland species than Murray cod. Artificial breeding programs being conducted for the species recovery use hormone injections to induce ovulation in naturally ripe fish in spring. Trout cod will hybridise with Murray cod and so for recovery projects it is important that Murray cod are not stocked into sites where Trout Cod and Murray cod are not already coexisting sympatrically.

Conservation

Trout cod were once common and abundant throughout the Murray-Darling Basin but are now listed on the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

as endangered due to overfishing, degradation of habitat and the introduction of invasive Trout species. The species is now totally protected. Only one wild, naturally occurring trout cod population remains in the Murray River in a region where the river is basically an extended transition zone from upland river habitat to lowland river habitat. In more lowland river habitats, river regulation and habitat degradation through activities like de-snagging, and overfishing, are probably the primary causes of decline. Heavy predation by introduced

redfin perch The European perch (''Perca fluviatilis''), also known as the common perch, redfin perch, big-scaled redfin, English perch, Euro perch, Eurasian perch, Eurasian river perch, Hatch, poor man’s rockfish or in Anglophone parts of Europe, simply th ...

, which were present in great numbers in the lowland reaches of the southern MDB for several decades, also played a large role in the decline of native fish in those reaches including trout cod. The possibility that trout cod populations in upland habitats were the ultimate source of trout cod populations in lowland habitats (i.e. source and sink populations) over long time frames (i.e. decades) cannot be discounted however. Historical accounts such as those from J.O.Langtry indicate lowland trout cod populations were secondary populations in secondary habitats, clearly in the minority to more abundant primarily lowland native fish species such as Murray cod, golden perch and silver perch. Therefore, it is doubtful whether strong trout cod populations can ever be established in lowland habitats, and therefore the issue of upland habitats, and the return of some upland habitats in trout-free form, needs to be addressed in trout cod conservation. Historical evidence indicates trout cod (and Macquarie perch) were abundant in most of the larger upland rivers and streams in the south-east corner of the Murray-Darling river system, and that these upland river habitats were their primary habitats. The extinction of trout cod populations in every one of its upland river habitats is an unresolved issue. Contrary to popular belief, many of these upland rivers still contain significant stretches of unregulated, high quality habitat. While dams, thermal pollution, siltation and other forms of habitat modification and degradation are responsible for the trout cod's extinction in many upland river habitats, it is almost certain that the reason for the trout cod's extinction in higher quality upland river habitats, that ''have not'' experienced serious modification and degradation, is the heavy domination of these habitats by introduced trout species, which are aggressive, predatory fish. Every single larger upland river and stream in south-eastern Australia is dominated by introduced trout species (rainbow trout and brown trout), with many having been continually stocked with introduced trout species for more than a century, and not a single larger upland river or stream in south-eastern Australia has been reserved in a trout-free state for larger upland native fish species. The effects of this course of action by fishery departments has been stark, and catastrophic events such as drought or bushfire, after which introduced trout species were restocked but upland native fish were not restocked, have shifted the balance further. The net result is that a number of upland native fish species including trout cod (and Macquarie perch) have completely died out or nearly so in their upland river habitats in the wild, apparently unable to cope with massive predation on their larvae/juveniles by introduced trout species and unable to cope with massive competition from introduced trout species for food and habitat at all life stages.

''I regret not knowing the name of a man I met at Tom Groggin Station, a Victorian property on the Indi River near Mt Kosciusko, who told me that he worked at Tom Groggin before he enlisted in the army and went to the first World War. He had fished the Indi before he left and it carried a great number of blue nose
rout cod A rout is a panicked, disorderly and undisciplined retreat of troops from a battlefield, following a collapse in a given unit's command authority, unit cohesion and combat morale (''esprit de corps''). History Historically, lightly-equi ...
white eye acquarie perchand greasies lackfish While he was at war, he even dreamt about fishing the Indi. When he came home he returned to his old job at Tom Groggin and announced that before he did any work, he wanted to go fishing. Very quickly he caught a fish about a foot (30cm) in length, the like of which he had never seen before. So intrigued was he by this strange spotted but nicely shaped fish that he immediately took it to the homestead thinking it was something quite unique. At the homestead, he was told it was a brown trout. From that time both the white eye acquarie perchand the blue nose
rout cod A rout is a panicked, disorderly and undisciplined retreat of troops from a battlefield, following a collapse in a given unit's command authority, unit cohesion and combat morale (''esprit de corps''). History Historically, lightly-equi ...
numbers went into decline, while the numbers of brown and rainbow trout increased. To my mind, this man did do something remarkable, he had set a very positive timeframe of a change over of fish species in the Indi River.'' ''Heads and Tales: Recollections of a Fisheries and Wildlife Officer.''

Scientific studies to document and quantify the impacts of introduced trout on trout cod (and Macquarie perch) in upland river habitats, and develop a more scientific approach to trout cod conservation and re-establishment efforts, including in upland river habitats, are desperately needed. Given the strong cultural cringe towards introduced trout in the wider community and the management bias towards introduced trout amongst fishery agencies these studies may be some way off. Two small populations of trout cod that have shown indications of breeding have been created by hatchery stockings in the lowland reaches of

Murrumbidgee River The Murrumbidgee River () is a major tributary of the Murray River within the Murray–Darling basin and the second longest river in Australia. It flows through the Australian state of New South Wales and the Australian Capital Territory, desce ...

at Gundagai and Narranderra, although it is far from clear whether these populations will be self-sustaining in the long term. Many other stockings of trout cod have failed, which is not surprisingly considering the small number of trout cod fingerlings stocked, and the fact that trout cod were frequently stocked into upland river habitats where introduced trout species were heavily entrenched, and in at least one case, were carried in conjunction with far larger stockings of introduced trout. A semi-natural population exists in a stretch of the very small upland Seven Creeks, which was established by translocations of trout cod (and Macquarie perch) above a set of falls in the 1920s. The Seven Creeks population is not a wholly artificial population, or a wholly unrepresentative habitat, as often claimed, as some of the trout cod translocated came — literally — from the base of the falls.

References

* * * Butcher, A.D. (1945) The food of indigenous and non-indigenous freshwater fish in Victoria, with special reference to ntroducedtrout. ''Fisheries Pamphlet 2''. Fisheries and Wildlife Department, Victoria. * Butcher, A.D. (1967) A changing aquatic fauna in a changing environment. ''IUCN Publications, New Series'' 9: 197–218. * Cadwallader, P.L. (ed.) (1977) J.O. Langtry's 1949–50 Murray River Investigations. ''Fisheries and Wildlife Paper.'' Ministry for Conservation, Victoria. * Cadwallader, P.L. (1979) Distribution of native and introduced fish in the Seven Creeks river system, Victoria. ''Australian Journal of Ecology'' 4: 361–385. * Cadwallader, P.L. & Gooley, G. (1984) Past and present distributions and translocations of Murray cod and trout cod in Victoria. ''Proceedings of the Royal Society of Victoria'' 96: 33–43. * Douglas, J.W.& Brown, P. (2000). Notes on successful spawning and recruitment of a stocked population of the endangered Australian freshwater fish, trout cod, Maccullochella macquariensis (Cuvier) (Percichthyidae). ''Proceedings of the Linnaean Society of N.S.W.'' 122: 143-147. * Merrick, J.R. & Schmida, G.E. (1984) ''Australian Freshwater Fishes; Biology and Management.'' Griffin Press, Australia. * Rhodes, J.O. (1999) ''Heads and Tales: Recollections of a Fisheries and Wildlife Officer.'' The Australian Deer Research Foundation Ltd, Melbourne. * Trueman, W. and Luker, C. (1992) Fishing Yesteryear. ''Freshwater Fishing Australia Magazine'' 17: 34–38. * Trueman WT (2007). Some recollections of native fish in the Murray-Darling system with special reference to the trout cod (Maccullochella macquariensis). Summary and source material for the draft publication ‘True Tales of the Trout Cod’. Native Fish Australia (Victoria) Incorporated, Doncaster, Victoria. Available online at: https://web.archive.org/web/20080721002731/http://www.nativefish.asn.au/files/Recollections_compressed.pdf * Trueman WT (2011). True Tales of the Trout Cod: River Histories of the Murray-Darling Basin. Publication No. 215/11. Murray-Darling Basin Authority, Canberra. Also available online at: https://web.archive.org/web/20130807212235/http://australianriverrestorationcentre.com.au/mdb/troutcod/

External links

* Native Fish Australi
Trout cod page
* Australian Government Department of the Environment and Heritage

* Australian Museum

* New South Wales Department of Primary Industries
cod recovery plan
* New South Wales Department of Primary Industries
cod fishnote
*Sepkoski, Jac
Sepkoski's Online Genus Database

Paleobiology Database
* Description (in French) ''Grystes Macquariensis'', "le growler de la rivière Macquarie"
p. 58
in Cuvier and Valenciennes ''Histoire naturelle des poissons'', tome 3. * Illustrations: figure 2 o
plate 12
in Griffith & Smith 1834. {{Taxonbar, from=Q2711806 trout cod Fish of the Murray-Darling basin Endangered fauna of Australia Taxa named by Georges Cuvier Extant Pliocene first appearances trout cod