The two-spined blackfish (''Gadopsis bispinosus'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

temperate perch 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 ...

endemic to

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is found in the cool, clear, strong-flowing, cobble bottomed, sub-alpine rivers and streams (ranging from small to large) in the southeast corner of the

Murray Murray may refer to: Businesses * Murray (bicycle company), an American manufacturer of low-cost bicycles * Murrays, an Australian bus company * Murray International Trust, a Scottish investment trust * D. & W. Murray Limited, an Australian who ...

- Darling river system. Their range encompasses northeast

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 ...

, southeast

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 ...

and the

Australian Capital Territory The Australian Capital Territory (commonly abbreviated as ACT), known as the Federal Capital Territory (FCT) until 1938, is a landlocked federal territory of Australia containing the national capital Canberra and some surrounding townships. ...

. Originally two-spined blackfish co-inhabited many of these waters with

Macquarie perch The Macquarie perch (''Macquaria australasica'') 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 (''Macquaria ambigua''). The ...

and

trout cod The trout cod (''Maccullochella macquariensis'') or bluenose cod, is a large predatory freshwater fish of the genus ''Maccullochella'' and the family Percichthyidae, closely related to the Murray cod. It was originally widespread in the south ...

. Two-spined blackfish are similar in shape and appearance to

river blackfish The river blackfish (''Gadopsis marmoratus'') is a freshwater fish endemic to the temperate waters of south-eastern Australia. It is found from southern Queensland through to central Victoria, including in the Murray- Darling river system. It ...

, though their spiny

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

usually contain only two spines (hence their scientific name) in comparison to river blackfish which have 7 to 13 distinguishable spines in their spiny dorsal fin. (In reality, this is a rather academic point as two-spined blackfish have blurred the difference between the dorsal spines and the dorsal rays that make up their soft dorsal fin, and any distinctions between the two weakly calcified dorsal spines and the dorsal rays that follow it are hard to pick in a living specimen.) The two-spined blackfish is similar to the river blackfish in spawning and diet; however, they prefer rocks and the interstices ("gaps") between to timber as the main spawning and habitat sites. Two-spined blackfish are also much smaller, commonly 15 to 17 cm and a maximum size of 30 cm. The species feeds mostly on aquatic insect larvae and terrestrial invertebrates, and occasionally other fishes and crayfish. Two-spined blackfish breed between October and December. Larvae hatch after around 16 days and remain at the spawning site with the male parent for another 3 weeks. Two-spined blackfish have declined seriously due to stream siltation and competition by introduced species, particularly introduced trout species. The species suffers serious predation and competition from introduced species of

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...

but due its nocturnal habits and cryptic, cover-oriented behaviour it appears to survive in sufficient numbers to maintain populations in high quality habitats. Recent severe bushfires in south-eastern Australia (2003–2006), however, have filled many upland rivers with large quantities of silt, and infilled the interstices ("gaps") between larger rocks that two-spined blackfish normally use as a refuge from predatory trout species. The presumed result will be increased levels of trout predation on two-spined blackfish and the long-term future of two-spined blackfish 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 Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

and localised extinctions.

References

External links

Native Fish Australia - Two-Spined Blackfish page
{{Taxonbar, from=Q6431588

two-spined blackfish The two-spined blackfish (''Gadopsis bispinosus'') is a species of temperate perch endemic to Australia. It is found in the cool, clear, strong-flowing, cobble bottomed, sub-alpine rivers and streams (ranging from small to large) in the southe ...

Freshwater fish of Australia