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Trout cod or bluenose cod, ''Maccullochella macquariensis'', is a large predatory freshwater fish of the ''Maccullochella'' genus and the Percichthyidae family, closely related to the Murray cod. It was originally widespread in the south-east corner of the Murray-Darling river system in Australia, but is now endangered.〔 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. In some parts of New South Wales 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.) 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 ''Maccullochella'' genus can be found from Miocene age (from about 23.03 to 5.332 million years ago) to recent age, while the species ''Maccullochella macquariensis'' is present from Lower Pliocene (3.6–5.3 mya) to recent age. ==Description== Trout cod have been reliably recorded to at least 80 cm and 16 kg, but there are some credible anecdotal accounts of larger specimens. Trout cod are broadly similar to the Murray cod, however there are some distinct differences in morphology and colouration. Trout cod are a small to medium groper-like fish with a deep, elongated body that is round in cross section. In contrast to Murray cod, trout cod have a pointed head with the top jaw overhanging the bottom jaw, and the slope of the head is straight. The eyes are slightly larger and more prominent than in Murray cod. The head tends to be free of speckling however a distinct dark stripe through the eye is usually present. Trout cod are cream to light grey on their ventral (“belly”) surfaces. Their back and flanks are most commonly bluish-grey in colour, overlain with irregular black speckling, but this can be highly variable depending on the habitat specimens come from, and can range from almost white to light grey-green, light brown, dark brown or almost black. The black speckling on the back and flanks is consistent however. 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 light grey to dark 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 and set forward of the pectoral fins. The leading white-coloured rays on the pelvic fins split into two trailing white filaments, while the pelvic fins themselves are usually a translucent cream or light grey. Smaller trout cod tend to be more slender than equivalent sized Murray cod; curiously, very large trout cod appear to develop deeper shoulders than equivalent sized Murray cod. While trout cod were only conclusively described as a separate species to Murray cod in 1972, commercial and recreational fishermen and early fishery biologists were in no doubt that there were two separate species of cod in the Murray-Darling system from the 1850s onwards, and noted the trout cod's different appearance and spawning biology and preference for cooler, faster flowing water and upland 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 — 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「trout cod」の詳細全文を読む スポンサード リンク
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