Spear tooth shark
| Spear tooth shark | ||||||||||||
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Spear-toothed shark habit |
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| Glyphis glyphis | ||||||||||||
| ( Müller & Henle , 1839) |
The spear tooth shark ( Glyphis glyphis ) is a type of river shark ( Glyphis ) within the Requiem shark (Carcharhinidae) with an only very vaguely defined range in the Indo-Pacific . Very little information is available about the shark, since the specimens of the spear tooth shark described differ significantly in the number of vertebrae, it is not fully clear whether it is one species or several. Compagno et al. a. In 2005 three more, as yet undescribed species of the genus assume in the area of the Indo-Pacific.
Appearance and characteristics
The spear tooth shark is a medium-sized to large shark with a maximum body length of at least 100 cm, body lengths of up to 300 cm are assumed. His back is gray-brown and has no noticeable markings.
The shark has a broad and rounded snout and very small eyes with nodding skins . It has an anal fin and two dorsal fins . The first dorsal fin is very broad and sickle-shaped at the base, it lies above or slightly behind the center of the pectoral fin base. There is no interdorsal ridge . The second dorsal fin is comparatively small and is opposite the anal fin. The pectoral fins are relatively large. Like all species of the genus, the animals have five gill slits and no injection hole .
Way of life
The spear tooth shark is a freshwater species that is likely to be found mainly in larger river areas of the Indo-Pacific region, but also penetrates into the brackish water zones of the river delta. It feeds predatory on various bony fish .
The adult specimens of the Australian population migrate from the sea to the estuaries of a few river systems in Northern Australia to mate. The offspring are born alive there between the end of October and December. The occurrence of juvenile fish is limited to a few river systems in the Australian Northern Territories and Queensland, for example around Cape York. The young are completely independent after birth and migrate upstream. There they spend the next three to six years at a distance of about 40 to 80 kilometers from the river mouth - in water with a reduced salt content (brackish water). "
During the annual monsoons, the fry migrate downstream in order not to expose themselves to the increasing influx of fresh water. As soon as the inflow of fresh water into the river systems ceases, and the salinity increases again and the values preferred by the young fish are reached again, they return to their original upstream locations.
It is currently unknown where exactly the adult sharks of the Australian population migrate when they leave the river systems. It is assumed that these are outside of the breeding season in the marine environments off the North Australian coast.
Reproduction
Like other species of the genus, it is probably viviparous and forms a yolk sac placenta ( placental viviparous ). The young sharks have a size of about 55 to 60 centimeters. The animals reach sexual maturity at a length of about 180 cm. Mating and birth of the Australian spear tooth shark takes place in the brackish estuary of a few river systems in the Northern Territories and Queensland, for example around Cape York. The young are born alive from the end of October to December.
distribution
The spear tooth shark lives in a very vaguely defined range in the Indo-Pacific around the Indonesian islands, New Guinea and Australia . Since the specimens of the spear tooth shark described differ significantly in the number of vertebrae, it is not fully clear whether it is one species or several. Compagno et al. a. In 2005, three more, as yet undescribed species assumed in the Indo-Pacific, of which Glyphis garricki was described in 2008 by Compagno, White and Last and the Borneo river shark ( Glyphis fowlerae ) in 2010 by Compagno, White and Cavanagh.
Danger
The spear tooth shark is classified as endangered in the IUCN Red List because there is no precise information about its range and way of life. It is believed that the species is very rare. The total population is estimated at 250 to 2500 individuals. The Australian spear tooth shark population is listed as critically endangered in the Environment Protection and Biodiversity Conservation (EBPC) Act. The number of female Australian spear tooth sharks is estimated to be less than 500 on the basis of the juveniles found.
Research history
In Australia, the spear tooth shark was first spotted in 1982 in the Bizant River near Lakefield. Until 2015 only young animals were caught. The catches are only ever made between the end of October and December.
In 2004 the Australian research agency CSIRO initiated long-term research with the aim of better understanding the distribution of juvenile fish in river systems in Tropical Australia. Since 2006, the CSIRO research group led by Dr. Richard Pillan's compiled data on migratory behavior and population status of juvenile spear tooth sharks in the Wenlock River.
In 2015, Dr. Pillans, Barry Lyon and Luke Burnett (Australian Zoo), within 9 days of intensive search to catch two adult spear-tooth sharks alive, a 2.2-meter-long female and a 2.3-meter-long male: the first find, according to CSIRO adult specimens of this species in Australia and the first living specimens ever to be caught by researchers. Before they were released, the two specimens were fitted with satellite-based transmitters, which automatically detach themselves from the body after 2 months and, during this period, transmit data on the water depth and water temperature in addition to the hiking route.
supporting documents
Evidence cited
- ↑ a b c d e f g h i Prometheus.tv Adult spear tooth sharks caught in Australia for the first time
- ↑ Compagno u. a., pp. 309-312.
- ↑ LJV Compagno, WT White, PR Last: Glyphis garricki sp. nov., a new species of river shark (Carcharhiniformes: Carcharhinidae) from northern Australia and Papua New Guinea, with a redescription of Glyphis glyphis (Müller & Henle, 1839) . In: PR Last, WT White, JJ Pogonoski (Ed.): Descriptions of new Australian Chondrichthyans . CSIRO Marine and Atmospheric Research, 2008, ISBN 978-1-921424-18-2 , pp. 203-226 .
- ↑ LJV Compagno, WT White, RD Cavanagh: Glyphis fowlerae sp. nov., a new species of river shark (Carcharhiniformes; Carcharhinidae) from northeastern Borneo. In: PP Last, WT White, JJ Pogonoski (Ed.): Descriptions of new sharks and rays from Borneo. (CSIRO Marine and Atmospheric Research Paper no. 32), pp. 29-44. ( Full text ; PDF; 7.6 MB)
- ↑ Data sheet from the Australian Department of the Environment, Water, Heritage and the Arts, Canberra
- ↑ Glyphis glyphis (Speartooth Shark). Retrieved October 15, 2018 .
literature
- Leonard Compagno , Marc Dando, Sarah Fowler: Sharks of the World . Princeton University Press , Princeton / Oxford 2005, ISBN 0-691-12072-2 , p. 310.
Web links
- Species portrait on hai.ch
- Spear tooth shark on Fishbase.org (English)