SIDHAT AUSTRALIA - Australian Eel - 澳洲鳗鲡
 |
 Short-finned eel, Anguilla australis Richardson, 1841新澳鰻鱺; 澳洲鳗; 黑鳗  Anguilla australis australis 澳洲鰻鱺  Anguilla australis occidentalis 短鰭澳洲鰻鱺  Speckled longfin eel, Anguilla reinhardtii Steindachner, 1867雷恩東澳鰻; 寬鰭鰻鱺 |
Australian EelsCongers Spotted Garden Eel |
| 學名 | Anguilla australis |  |
| 命名者 | Richardson, 1841 | |
| 中文名 | 澳洲鰻鱺 | |
| 科中文名 | 鰻鱺科 | |
| 科名 | Anguillidae | |
| 中文俗名 | 黑鰻、澳洲鰻、短鰭鰻 | |
| 英文俗名 | Shortfin eel | |
| 型態特徵 | 身體延長呈圓筒狀。頭小。口裂可達眼睛下方。鱗片細小不明顯，且深埋於皮膚下方。背部呈黃綠至灰黑色，體側為暗綠色，腹部顏色較淡。背鰭起點位於臀鰭起點不遠；胸鰭軟條數為14-16。脊椎骨數為109-116。最大體長可達90公分。 | |
| 棲所生態 | 棲息於溪流、湖泊或沼澤地，特別是溪流中的緩流區與潭區。以魚類、甲殼類及軟體動物為食，有時亦會吞食水生植物。 | |
| 地理分布 | 廣泛分佈於西太平洋群島，包含大溪地、斐濟、紐西蘭、聖誕島及澳洲西南部等地。 | |
| 漁業利用 | 澳洲鰻於產地被當做極佳的釣遊魚種。肉質美味。 | |
| 備註 | ||
| ||
Short-finned eel (Anguilla australis)
DescriptionLong, tubular body with dorsal, tail and anal fins forming one fin. Small gill opening on each side of the head. Large mouth extending to below the small eye. vertical gill openings. Dorsal fin begins just forward of the anal fin. Back and sides may be olive-green or vary from pale green to olive-brown, sometimes with coppery tints above and silvery sides. Belly is greyish to silvery-white. Fin colour is dark like the back. DistributionCommon and widespread in Victoria south of the Great Dividing Range, occurring occasionally in northern streams draining into the Murray River. HabitatPrefers low-lying swampy streams and lagoons. Although it occurs in a wide variety of habitats it is essentially a still-water species. Common in many southern Victorian lakes. Studies of tagged eels indicate that maturing adults in freshwater establish home ranges of about 400 m. Brief BiologyKnown to occur in Victoria to 1.1 m and 6.8 kg, but is usually smaller. Appears to go into hibernation if water temperature falls below 10°C. Hibernating or otherwise there are records of eels going without food for up to 10 months. Opportunistic omnivore although it is primarily carnivorous. Adult eels are known to take fish of various types, worms, insects, small crustaceans, molluscs and water plants. Feeding appears to follow a seasonal pattern, being most intense at night in shoreline shallows during spring and summer. Mature migrating adults vary from 6 to 24 years of age, spending up to 14 years in freshwater. Spends most of its life cycle in freshwater and migrates downstream to spawn at sea when sexually mature. General information for Victorian freshwater eel speciesOne of the most interesting features of Victorian freshwater eels, is the huge migration they make to a spot somewhere south east of New Guinea in the Coral Sea. This is the sole spawning site for all Australian and New Zealand freshwater eels, with some eels having to travel in excess of 3,000 kilometres to get there. They begin their lives at this spawning site, at a depth of 200 m, as tiny transparent larvae. They are carried southwards by the ocean currents that parallel the east coast of Australia, and swing east past Tasmania and then north to New Zealand. Along the way, they feed on microscopic organisms and develop into transparent, leaf-shaped larvae or leptocephali and eventually metamorphose into 'glass eels' which are eel-shaped, but extremely small and still transparent. At this stage, they move closer to land and commence migrating towards estuaries. The ability of eels to reach Victorian waters is believed to be dependent on the formation of relatively erratic eddy currents, which split off from the main east Australian current and transport the developing larvae through Bass Strait. These currents break down before they reach the mouth of the Murray River and this is the reason for the natural absence of eels in the Murray River and its tributaries north of the Great Dividing Range. In years when these currents are strong, there is a massive arrival of glass eels along the Victorian coast, but in some years the currents are weak and very few glass eels arrive. Their attraction to an estuary depends on the ability of glass eels to detect freshwater flows from rivers. In years when river flows are low and estuaries may even be closed, recruitment of glass eels is correspondingly reduced or may be zero. Short-finned glass eels enter estuaries mainly during mid winter to late spring, while long-finned glass eels enter estuaries from mid summer to late autumn. Short-finned eels spread along the entire Victoria coastline, while long finned eels are only found east of Wilsons Promontory. Some glass eels will quickly pass through the estuary and migrate upstream and others will remain in the estuaries for some time. They all gradually take on the dark pigmentation of freshwater eels and at this time they are known as elvers. Some elvers remain in the estuary until they mature, but most will migrate upstream in secondary migrations, known as “eel fares”, which involve glass eels and elvers of several age groups moving inland into rivers, creeks, lakes and swamps. Male short-finned eels generally mature when eight to twelve years of age, whilst females mature in ten to twenty years and long-finned eels can take double this time to mature. At maturity, eels undergo a number of changes in preparation for the spawning migration. After a period of voracious feeding, and significant growth, their eyes become larger and their skin takes on a silvery appearance. Internally, their gonads begin to develop and their digestive system closes down and starts to degenerate, Now known as 'silver' eels, they migrate back to the sea during late summer and autumn. They quickly move into deeper water and in total darkness swim north against the current to reach the Coral Sea. By the time they arrive, they have basically used up all their energy resources and are little more than a skeleton with gonads. They spawn and die and their young commence the cycle over again. The commercial fishery for eels utilises both species, in coastal waters from Mallacoota to Portland. However, the bulk of the activity is based on short-finned eels and takes place in the lakes and wetlands of the Western District. Much of the production depends on the eel fishers translocating large numbers of small eels from waters where conditions for growth are poor, to more favourable areas where they can grow to reach commercial size and condition over a number of years. With a fishery that involves such a slow growth rate, a long life cycle, and where recruitment is so erratic and variable, it would be very easy for the stock to be overfished and for the fishery to collapse for long periods. This has not happened because entry to the fishery is tightly controlled, and the best waters have been exclusively allocated to individual fishers. This encourages each operator to fish their water conservatively and ensures that, if they exercise restraint, they will be the one getting the benefit of it. In addition to this, there are many coastal streams that are totally closed to commercial eel fishing. Although this was done initially to ensure that platypus in these waters were not caught in nets, it also ensures that there is always an unexploited area to provide spawning stock to return to the sea. There is a huge unsatisfied world demand for glass eels for aquaculture, and without tight control, the Australian resource could be quickly stripped to satisfy European and Asian requirements. While the average angler may have little regard for the common eel, it certainly has a fascinating life cycle, and supports a significant and productive commercial fishery. When it is also considered how intensively anglers use many of the waters important to the commercial eel fishery, there has been a commendable lack of conflict between the two groups. |
Anguilla australis occidentalis - 短鳍澳洲鳗鲡 |
Eels (Anguilla Reinhardtii) At Tarzali Lakes we specialise in Longfin Eels (Anguilla reinhardtii), a subtropical species that is distributed from northern Queensland down through to the north-eastern tip of Tasmania. Some of our eels are naturally occurring on our property. Our juvenile eels are destined for overseas markets, in particular China. Of course, we reserve for our local customers some of our best stock as live fresh or in-house smoked. Eels have been regarded as mysterious creatures since ancient times, and numerous theories have been put forward over the years about how they breed and what their movements are. Their exact life history is still a point of debate among scientists. As yet, none have been bred to full size in captivity. Eels are catadromous (that is, they live in freshwater but migrate to saltwater for reproduction). They spawn in the Coral Sea waters at depths greater than 300 metres. Each female can produce 5-10 million pelagic eggs, which are carried to the continental shelf by ocean currents where they develop into -glass eels which are toothless and unpigmented. The glass eels move into estuaries with the assistance of currents and tides and after one to three years grow into elvers as they develop pigmentation. As elvers they then continue the migration into lakes and rivers and other accessible water bodies. Male eels longer than 0.5m are rare. Females up to 1m long are common and occasionally they may reach lengths of 1.5m and weights of up to 4kg. Exceptionally large specimens have been recorded weighing up to 8kg. |
The speckled longfin eel or Australian long-finned eel, Anguilla reinhardtii, is one of 15 species of eel in the family Anguillidae. It has a long snake-like cylindrical body with its dorsal, tail and anal fins joined to form one long fin. It usually has a brownish green or olive green back and sides with small darker spots or blotches all over its body. Its underside is paler. It has a small gill opening on each side of its wide head, with thick lips. It is Australia's largest freshwater eel, and the female grows much larger than the male. It is also known as the spotted eel.
DistributionThe long-finned eel is a native of New Guinea, eastern Australia (including Tasmania), Lord Howe Island, and New Caledonia. Specimens have been found in some Pacific islands and in New Zealand. It can be found in many freshwater areas, including creeks, streams, rivers, swamps, dams, lagoons, and lakes. Size and lifespanLong-finned eels can grow to 2 metres (6 feet) for males and 1.58 metres for females, although landlocked eels can grow to 3 metres (10 feet) and weigh 20 kilograms (more than 40 pounds). They can live more than 100 years. Breeding and migrationReferences
|
Tidak ada komentar:
Posting Komentar