River blackfish

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River blackfish
Gadopsis marmoratus by Arthur Bartholomew.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Percichthyidae
Genus: Gadopsis
Species:
G. marmoratus
Binomial name
Gadopsis marmoratus

The river blackfish (Gadopsis marmoratus) is a freshwater fish endemic to the temperate waters of south-eastern Australia. [2] It is found from southern Queensland through to central Victoria, including in the Murray-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 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. It is a popular angling fish in some parts of its range. [2]

Contents

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 fin 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 an ambush predator that takes crayfish, shrimp, small fish and aquatic insects. [2] 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 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 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 (12 lb). 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.[ citation needed ] The taxonomy does not yet reflect to 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. 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.

Conservation

Blackfish have declined very seriously due to overfishing, stream siltation and snag removal, and predation and competition by introduced species, 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. [2]

Related Research Articles

<span class="mw-page-title-main">Murray cod</span> The largest Australian predatory freshwater fish in the family Percichthyidae

The Murray cod is a large Australian predatory freshwater fish of the genus Maccullochella in the family Percichthyidae. Although the species is called a cod in the vernacular, it is not related to the Northern Hemisphere marine cod (Gadus) species. The Murray cod is an important part of Australia's vertebrate wildlife—as an apex predator in the Murray-Darling River system—and also significant in Australia's human culture. The Murray cod is the largest exclusively freshwater fish in Australia, and one of the largest in the world. Other common names for Murray cod include cod, greenfish, goodoo, Mary River cod, Murray perch, ponde, pondi and Queensland freshwater cod.

<span class="mw-page-title-main">Eastern freshwater cod</span> Species of fish

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<span class="mw-page-title-main">Trout cod</span> Species of fish

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<span class="mw-page-title-main">Macquarie perch</span> Species of fish

The Macquarie perch 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.

<span class="mw-page-title-main">Golden perch</span> Species of fish

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The Australian bass is a small- to medium-sized species of primarily freshwater fish found in coastal rivers and streams along the east coast of Australia. A member of the genus Macquaria from the family Percichthyidae, the Australian bass is an important member of the native fish assemblages found in east coast river systems. It is a native predatory fish and an extremely popular game fish species among anglers. The species was simply called perch in most coastal rivers where it was caught until the 1960s, when the name "Australian bass" started to gain popularity.

<span class="mw-page-title-main">Two-spined blackfish</span> Species of fish

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<i>Bidyanus bidyanus</i> Species of fish

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<i>Galaxias olidus</i> Species of fish

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<i>Galaxias</i> Genus of fishes

Galaxias is a genus of small freshwater fish in the family Galaxiidae, and are frequently referred to as the galaxiids. These highly adaptable fish are typically found at temperate latitudes across the Southern Hemisphere.

<i>Gadopsis</i> Genus of fishes

Gadopsis is a genus of temperate perches endemic to freshwater habitats in southeastern Australia. The genus was formerly considered to be in a family of its own, Gadopsidae.

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<span class="mw-page-title-main">Bony bream</span> Species of fish

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<span class="mw-page-title-main">Murray River rainbowfish</span> Species of fish

The Murray River rainbowfish, known less commonly as the Australian rainbowfish, is a species of freshwater fish endemic to southeastern Australia. The southernmost species of all rainbowfishes, these fish are very colourful, hence the name; and there is sexual dimorphism with the males being larger and more colourful than females. Murray River rainbowfish are schooling fish and will congregate near logs or riverbanks, and are a popular aquarium fish.

<span class="mw-page-title-main">Southern pygmy perch</span> Species of fish

The southern pygmy perch, also known as the Tasmanian pygmy perch, is a species of freshwater ray-finned fish, a temperate perch from the family Percichthyidae which is native to south-eastern Australia and Tasmania.

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References

  1. Lintermans, M.; Freeman, R.; Unmack, P.; Raadik, T. (2019). "Gadopsis marmoratus". IUCN Red List of Threatened Species . 2019: e.T123358463A123382771. doi: 10.2305/IUCN.UK.2019-3.RLTS.T123358463A123382771.en . Retrieved 20 November 2021.
  2. 1 2 3 4 Bray, Dianne. "River Blackfish, Gadopsis marmoratus". Fishes of Australia. Retrieved 3 September 2014.