Australian grayling | |
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A relatively small Australian grayling caught and released on a dry fly. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Osmeriformes |
Family: | Retropinnidae |
Genus: | Prototroctes |
Species: | P. maraena |
Binomial name | |
Prototroctes maraena Günther, 1864 | |
The Australian grayling (Prototroctes maraena) is a primarily freshwater fish found in coastal rivers in south-eastern mainland Australia and Tasmania. In past decades it has also been known as the cucumber mullet or cucumber herring, for its cucumber-like odour.
The Australian grayling is a streamlined fish with a long and slender body and small conical head. [2] Colouration is usually silver on the flanks and dusky olive on the back, overlain with a gold sheen. [3]
Australian grayling commonly live for 2–3 years and reach around 20 centimetres (7.9 in) in length, although rare individuals have been recorded up to at least 5 years in age and 33 centimetres (13 in) in length. [3] The fish has an omnivorous diet, feeding upon algae, shrimp, and small insects. They have specially adapted teeth and a long gut to help with the digestion of algae. [2]
Australian grayling spawn in the freshwater reaches of coastal rivers. Spawning is thought to occur in late autumn or early winter. McDowall (1996) reports that egg counts range from 25,000 to 67,000 in females 170–200 mm long, and that the small (~1 mm) demersal eggs probably settle among gravel and cobble in the river bed before hatching. Hatched larvae are washed out to sea. Australian grayling juveniles return to the freshwater reaches of rivers after roughly 6 months at sea and spend the rest of their lives in river habitats. [3]
Before the introduction of exotic fish species including the Eastern mosquitofish and trout to Australian waterways the Australian grayling and spotted galaxias were keenly fished by recreational anglers using fly-fishing gear. [2] The species was appreciated for its willingness to take wet and dry flies, its excellent fighting ability on very light tackle, and its relatively large size. However, due to declining numbers the fish is now protected under the Environment Protection and Biodiversity Conservation Act 1999. [2] Heavy penalties apply for taking any of the fish.
Australian grayling suffered massive initial declines in 1868–70 through very large, unexplained fish kills (Saville-Kent, 1888). Australian grayling killed in these events are described as being covered in "cottony growths", a characteristic hallmark of the exotic fungus-like oomycete Saprolegnia ; these kills likely mark the arrival of this exotic pathogen in Australian freshwater habitats via the importation, culturing and stocking of exotic salmonid species. [4]
Saville-Kent then went on to consider the apparent epidemic some 17–18 years previously which had caused the demise of the Australian grayling Prototroctes maraena. The grayling were said to "have been seen floating down the rivers in thousands, covered more or less extensively with a cottony fungoid growth. So virulent and exhaustive was this epidemic that many, more especially of the southern rivers, were more or less completely denuded of their stock of this species and have so remained up to the present date". Saville-Kent posed the questions of how, when and where the epidemic originated and whether at the time there were any abnormal conditions associated with the rivers carrying the infected fish. He went on to say: "The approximate date of the appearance of this epidemic would appear to be about the year 1869 or 1870, periods it may be remarked of great activity in association with the distribution of the fry of the newly acclimatised Salmonidae in the rivers of this colony. Is it possible ... that the fungus, ‘’Saprolegnia’’, was hitherto unknown to Tasmania and was introduced with the ova of these Salmonidae, or more probably in the moss wherein they were packed? Under such conditions the germs or spores, like the microbes of measles or smallpox, arriving on a virgin and congenial soil, might be expected to spread with devastating virulence among the aboriginal inhabitants." [5]
Australian grayling is threatened by a number of factors. Dams and weirs block migration and also block floods and reduce base flows, both of which are important for habitat maintenance and for spawning and movement of grayling larvae and juveniles to and from the sea. Irresponsible forestry and farming practices degrade and fragment river environments through siltation and other effects. Exotic trout species threaten grayling through predation and competition. Scientific studies have shown native fish species similar in habitat and lifestyle such as spotted galaxias are severely depressed in number in rivers inhabited by exotic trout species (Ault & White, 1994), and are forced into sub-optimal feeding locations, feeding times and diets by aggressive competition from exotic trout species (McDowall, 2006). A chronic lack of exotic-trout-free habitat reserved for galaxias species and other native fish species in south-eastern Australia generally is a major concern. [6] [7]
Two Australian grayling were observed in the Glenelg River in south-western Victoria in early 2021, the first recorded sighting since 1899. Scientists think that some of the environmental degradation caused after agriculture was introduced into the area was being reversed, and the health of the river and estuary has improved enough for the fish to make a comeback. [8]
Australian grayling are listed as a vulnerable species under Australia's Environment Protection and Biodiversity Conservation Act 1999 and under the IUCN Red List. [2] There are now a number of conservation measures focused on conserving the fish.
Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes, consisting of 11 extant genera and over 200 species collectively known as "salmonids". The family includes salmon, trout, char, graylings, freshwater whitefishes, taimens and lenoks, all coldwater mid-level predatory fish that inhabit the subarctic and cool temperate waters of the Northern Hemisphere. The Atlantic salmon, whose Latin name became that of its genus Salmo, is also the eponym of the family and order names.
Thymallus thymallus, the grayling or European grayling, is a species of freshwater fish in the salmon family Salmonidae. It is the only species of the genus Thymallus native to Europe, where it is widespread from the United Kingdom and France to the Ural Mountains in Russia, and Balkans on the south-east, but does not occur in the southern parts of the continent. It was introduced to Morocco in 1948, but it does not appear to have become established there.
Saprolegnia is a genus of water moulds often called cotton moulds because of the characteristic white or grey fibrous patches they form. Current taxonomy puts Saprolegnia as a genus of the heterokonts in the order Saprolegniales.
The Galaxiidae are a family of mostly small freshwater fish in the Southern Hemisphere. The majority live in Southern Australia or New Zealand, but some are found in South Africa, southern South America, Lord Howe Island, New Caledonia, and the Falkland Islands. One galaxiid species, the common galaxias, is probably the most widely naturally distributed freshwater fish in the Southern Hemisphere. They are coolwater species, found in temperate latitudes, with only one species known from subtropical habitats. Many specialise in living in cold, high-altitude upland rivers, streams, and lakes.
The climbing galaxias or kōaro is a fish of the family Galaxiidae found in Australia, New Zealand, and nearby islands. The name climbing galaxias is used in Australia, and koaro or kōaro in New Zealand. Further vernacular names include short-finned galaxias, broad-finned galaxias, Cox's mountain galaxias, and Pieman galaxias.
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.
The mountain galaxias is a species complex of freshwater galaxiid fish found all over southeast Australia.
The common galaxias or inanga is a very widespread Southern Hemisphere fish in the family Galaxiidae. It is a slim, narrow fish with a forked tail and a mottled, spotty pattern, typically about 10 cm (4 in) long when fully grown. It lives in fresh water, but spawns at river mouths and spends the first six months of its life at sea, returning en masse in spring. Its vernacular names include cowfish, jollytail, common jollytail, eel gudgeon, inaka, native trout, pulangi, puye, slippery tarki, spotted minnow, Falklands minnow and whitebait.
Galaxias olidus, the mountain galaxias, is a species of freshwater galaxiid fish widely found in southeastern Australia.
Eldon's galaxias is an endangered galaxiid fish endemic to New Zealand. One of several fishes in the genus Galaxias found in Central Otago, it has a very small home range and is at risk of being driven to extinction by trout introduced for recreational fishing.
The common river galaxias or Canterbury galaxias is a galaxiid fish of the genus Galaxias, found only in Canterbury, New Zealand.
The New Zealand grayling is an extinct species of fish that was endemic to New Zealand. It was known to the Māori by many names, including pokororo, paneroro, kanae-kura, and most commonly, upokororo. The variety of names for the fish came from either multiple tribes, or to describe the fish at different periods of its life cycle. Even though this fish is named grayling, it is not related to European or American graylings and lacks the large dorsal fin ‘typical’ graylings are characterised by. It is, however, closely related to the Australian grayling. The New Zealand grayling was an amphidromous species, migrating between freshwater and saltwater during different seasons as well as stages in their life cycle. The last sighting of the New Zealand grayling was in 1923, and it was declared extinct in 2018.
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.
The Cape galaxias is a species of freshwater fish of the family Galaxiidae.
Spotted galaxias is a largish, primarily-freshwater galaxias species found in southern Australia. Spotted galaxias are perhaps the most beautiful of the Australian galaxias species. They are a somewhat tubular, deep-bodied fish, with a dusky brownish-red colouration overlain with dark, haloed spots, dramatic black edges to dorsal, anal and pelvic fins, and a dark diagonal stripe through the eye.
Galaxias fontanus, the Swan galaxias, is a species of fish in the family Galaxiidae. It is endemic to eastern Tasmania, Australia.
Salmo dentex is a variety of trout, a freshwater fish in the family Salmonidae, found in the western Balkans. Until recently the identity, biological distinctness and species status of the dentex trout were not properly clarified, but genetic data now suggest it is not a monophyletic unit that could be distinguished from other salmonids as a separate species.
The Keurbooms River is a river in the Western Cape Province in South Africa. The river has its sources south of Uniondale in the Langkloof and flows in a roughly southeastern direction. It passes De Vlugt and the Prince Alfred Pass, flowing along the northern side of the R340 road then it turns south. After crossing the N2 road, it flows into the Indian Ocean through the Keurbooms Estuary, located close to the coastal town of Plettenberg Bay.
The Golden galaxias is an endangered species of landlocked galaxiid fish belonging to the genus Galaxias. It is endemic to Lakes Crescent, Sorell, and their associated waterways located in central Tasmania, Australia.
Robert Montgomery McDowall was one of New Zealand's most prominent freshwater ichthyologists.