Pangasius sanitwongsei
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Pangasius sanitwongsei |
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| Pangasius sanitwongsei | ||||||||||||
| Smith , 1931 |
Pangasius sanitwongsei is a species of fish from the shark catfish familyand, with a length of up to three meters, is one of the largest freshwater fish species in the world. She comes into the river systems Chao Phraya River and the Mekong in Southeast Asia and is due to overfishing and habitat loss as threatened with extinction . Within the shark catfish, the species is unusual because of its size and its diet as a predatory fish that also goes to larger prey. A common German name does not exist, but the species is sometimes referred to as high-finned shark , wolverine or Thai park , especially in aquaristics.
features
Pangasius sanitwongsei has the typical body structure of the shark catfish with a scaly, elongated and laterally flattened body. It differs from the other species in the family by its very broad head and the thread-like, elongated soft rays on the pectoral, abdominal, anal and dorsal fin. After the Mekong giant catfish ( Pangasianodon gigas ), Pangasius sanitwongsei is the largest species in the family. The longest scientifically measured specimen was two and a half meters long, but many authors consider older information of up to three meters or even more to be credible. The maximum weight stated is up to 300 kilograms. Animals of this extreme size are no longer found today, which is probably a consequence of the sharp decline in the population. The body is dull gray or dark greenish to almost black with a lighter belly. There is a light spot above the anal fin, as well as each of the pectoral fins; the latter can be related to the light abdominal color and do not occur in any other species of the genus. The dorsal, adipose and caudal fins are black, the pectoral and pelvic fins dark gray and the anal fin light with dark areas, the first rays having black tips, which are particularly pronounced in young animals.
The head and mouth of Pangasius sanitwongsei are very wide for a shark catfish, the head ends rounded to almost blunt. The eyes are small and set relatively low on the sides. The barbels are slender and relatively short, with the top pair being slightly longer. The teeth on the palatine bone and ploughshare bone form a single, crescent-shaped tooth field. The gill trap has 16 to 21 rays on the first arch. The number of vertebrae is 50 to 52, of which 21 to 23 are in the abdomen , which are both the highest numbers of all shark catfish. The swim bladder is two-chambered and lies completely in the abdomen.
The dorsal fin has two unbranched hard rays and seven branched soft rays. The second hard beam is slightly sawn at the back in the lower area and has a long filamentous extension so that it can reach half the total length of the head and trunk. The branched rays decrease increasingly in length, so that the fin is pointed triangular. In the pectoral and ventral fins, the outermost, hard ray has a long thread-like extension. In the case of the pectoral fins, this beam can reach up to 60 centimeters in length in large animals and is strong enough to lead to serious injuries if the animals are carelessly handled. The anal fin has four hard rays and 26 soft rays, the second hard ray again being elongated in a filamentous manner. In older animals in particular, the filamentous processes can also be missing, especially in the pectoral, ventral and anal fins, which is probably due to injuries.
Occurrence
The species is native to the Mae Nam Chao Phraya and the Mekong and their larger tributaries. Two populations probably exist in the Mekong, separated by the Mekong Falls , which the species, unlike most other shark rocks, does not cross. The southern population inhabits the river from the upper Mekong estuary near the Cambodia and Vietnam border to just below the Mekong Falls near the Cambodia and Laos border . The northern population lives in the stream above the Mekong Falls in Laos and Thailand, probably as far as Myanmar and southern China . Today, the natural occurrences of Pangasius sanitwongsei in the Chao Phraya and Mekong in Thailand have likely collapsed.
Way of life
Little is known about the way of life of Pangasius sanitwongsei . The adult fish are likely to stay exclusively in the main stream and larger tributaries without entering the floodplains in the rainy season, while younger fish also penetrate into smaller rivers near the main streams. In the dry season, the large animals retreat to deep pools at the bottom of the main stream, which they probably only leave to eat.
The animals are carnivores that feed primarily on fish and crustaceans, with migratory fish likely to make up the majority of the prey in older animals. Older animals also go to larger prey and driving carrion, which is unusual for shark catfish. The species is therefore sometimes called "dog-eating catfish" ( English for ' dog-eating catfish '). Young animals feed mainly on insects and insect larvae.
The breeding season is between May and July. In addition, the adult animals migrate from their dry season refuge upstream to the spawning areas. This hike is triggered by the falling water levels at the end of the rainy season. The exact spawning grounds are still unknown. The eggs are sticky and two to two and a half millimeters in diameter. After hatching, the young fish can be driven downstream. From mid-June, young animals with a length of about ten centimeters appear.
Relationship with people
There is evidence that Pangasius sanitwongsei played a role in various older Southeast Asian cultures. There is a relief in Angkor Wat that shows a large, scaly fish in a sacred pond devouring a four-legged animal. In Laos, the two large species of shark P. sanitwongsei and P. gigas were traditionally eaten after religious celebrations. The species is also otherwise used as food fish, with the quality being assessed differently by different authors. They are caught with nets and fishing rods, but due to their rarity they no longer play a role in fishing on the Mekong. Large animals were deliberately baited with poultry or dog carcasses and in some cases made unrecognizable by cutting off their fins before they were sold, since they would otherwise be more difficult to sell as scavengers. Due to its size and rapid growth, first attempts were made to raise the species in aquaculture . Occasionally the animals are also kept as aquarium fish, but as large predatory fish they are only suitable for very large show aquariums. In Aquarium Berlin more animals live in a six-meter pool. Due to its size and strength, the species is also popular with sport fishermen and is kept for this purpose in various "fishing parks" in Thailand.
Pangasius sanitwongsei is considered to be threatened with extinction in the wild and has already disappeared from parts of the original range. The main threat factor is overfishing, especially as edible fish and, to a lesser extent, as catch for aquariums. In addition, the species probably suffers from the loss of suitable habitats due to the expansion of the Mekong for shipping and the associated destruction of possible spawning areas, as well as the hindrance of migrations due to the construction of dams, which represent obstacles and change the flooding cycle of the river. In 1967 the population in the Chao Phraya was estimated at 2000 animals and within the last three generations the total population has collapsed by an estimated 99%. In 1989 Pangasius sanitwongsei was classified as a protected class II species by the provincial government of Yunnan (China) and it has been listed as Critically Endangered on the IUCN Red List since 2009 . In Thailand, artificially reproduced animals are abandoned as a conservation measure, although no genetically controlled breeding program exists. The greatest obstacle to effective protection of the species is that too little is known about its way of life, which is why, for example, targeted protection of the spawning areas is not possible.
Taxonomy and systematics
Pangasius sanitwongsei was first described scientifically in 1931 by Hugh McCormick Smith . In this work, however, two animals were described as separate species, which probably belong to the same species: Pangasius beani on the basis of a 15.3 cm long young animal, named after the assistant curator of the United States National Museum Barton Appler Bean , and Pangasius sanitwongsei based on a 61.3 cm long animal named in honor of Yai S. Sanitwongse , who brought Smith's attention to the species. Since Smith and the authors who followed him only used the name Pangasius sanitwongsei in almost all later works , this was recognized as a valid scientific name in the revision of the Pangasiidae by Roberts and Vidthayanon. Molecular biological studies show Pangasius sanitwongsei within the genus as a relatively derived species that is not particularly closely related to any of the other species. But they could not resolve the exact position within the genus. The evolutionary separation from the other species in the genus probably took place in the early Pliocene , about 5 million years ago.
literature
- Tyson R. Roberts, Chavalit Vidthayanon: Systematic revision of the Asian catfish family Pangasiidae, with biological observations and descriptions of three new species . In: Proc. Acad. Nat. Sci. Philad. tape 143 , 1991, pp. 97-144 (English).
Web links
- Pangasius sanitwongsei on Fishbase.org (English)
- Pangasius sanitwongsei in the Encyclopedia of Life
Individual evidence
- ↑ a b c d e Hugh McCormick Smith: Descriptions of new genera and species of Siamese fishes . In: Proceedings of the United States National Museum . tape 79 , no. 2873 , 1931, pp. 1–48 (English, full text (pdf; 4.0 MB) ).
- ↑ a b c d e f g Tyson R. Roberts, Chavalit Vidthayanon: Systematic revision of the Asian catfish family Pangasiidae, with biological observations and descriptions of three new species . In: Proc. Acad. Nat. Sci. Philad. tape 143 , 1991, pp. 97-144 (English).
- ^ A b Hugh McCormick Smith: The fresh-water fishes of Siam, or Thailand . In: Bulletin of the United States National Museum . tape 188 , 1945, pp. 363-365 (English).
- ↑ a b c d e Zeb Hogan, Uthairat Na-Nakorn and Heng Kong: Threatened fishes of the world: Pangasius sanitwongsei Smith 1931 (Siluriformes: Pangasiidae) . In: Environmental Biology of Fishes . tape 84 , no. 3 , 2009, p. 305-306 (English).
- ↑ a b c d A.F. Poulsen, KG Hortle, J. Valbo-Jorgensen, S. Chan, CKChhuon, S. Viravong, K. Bouakhamvongsa, U. Suntornratana, N. Yoorong, TT Nguyen, BQ Tran: Distribution and Ecology of Some Important Riverine Fish Species of the Mekong River Basin . In: MRC Technical Paper . No. 10 . Mekong River Commission, 2004, ISSN 1683-1489 , p. 98-102 (English, full text (pdf; 5.0 MB) ).
- ^ Walter J. Rainboth, Food and Agriculture Organization of the United Nations: Fishes of the Cambodian Mekong . Food and Agriculture Organization of the United Nations, 1996, ISBN 978-92-5103743-0 , pp. 157 .
- ^ Tyson R. Robert: Fish scenes, symbolism, and kingship in the bas-reliefs of Angkor Wat and the Bayon . In: The Natural History Bulletin of the Siam Society . tape 50 , no. 2 , 2002, p. 135–193 (English, full text (pdf; 5.1 MB) ).
- ↑ Eric Baran, Teemu Jantunen, Chiew Kieok Chong: Values of inland fisheries in the Mekong river basin . The WorldFish Center, 2007, pp. 13 .
- ^ Tim M. Berra: Freshwater Fish Distribution . 2nd Edition. University of Chicago Press, 2007, ISBN 978-0-226-04442-2 , pp. 179 .
- ↑ Hans A. Baensch , Hans-Georg Evers: Aquarium Atlas, Volume 6 . Mergus, Melle 2002, ISBN 3-88244-068-6 , pp. 651 .
- ^ Pangasius and fishing. In: www.pangasius.at. Retrieved April 19, 2012 .
- ↑ a b Pangasius sanitwongsei in the endangered Red List species the IUCN 2009. Posted by: Jenkins, A., Kullander, FF & Tan, HH, 2009. Accessed March 22, 2012th
- ↑ L. Pouyard, GG Teugels, R. Gustiano, M. Legendre: Contribution to the phylogeny of pangasiid catfishes based on allozymes and mitochondrial DNA . In: Journal of Fish Biology . tape 56 , 2000, pp. 1509-1538 (English).
