Common sawfish
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Common sawfish ( Pristis pristis ) |
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| Pristis pristis | ||||||||||||
| ( Linnaeus , 1758) |
The Common sawfish ( Pristis pristis ), and sawfish , Leichhardt's sawfish or heavy Thai called, is a kind of the family of sawfish (Pristidae). The fish can be over 6 meters long and reach a maximum age of over 50 years.
features
The common sawfish can grow to be over 6 meters long. There are also reports of 7 and 7.5 meter long specimens. The fish are monochrome brown on the back, the belly is whitish. The trunk is shark-like and elongated, cylindrical in cross-section at the top and clearly flattened on the ventral side. The trunk and tail stalk are not clearly separated from each other. The most striking feature is the strong, long, saw-like rostrum. The rostrum begins directly in front of the eyes (above) or nostrils (below) and becomes a little narrower towards the front. The tip of the rostrum is rounded. The distance between the eyes and the tip of the rostrum is 23.8 to 30.9% of the total length. There are 14 to 23 teeth on each side of the rostrum. The rostral teeth are evenly spaced apart, only at the tip they are a little closer. The head is flattened and broad. The spray holes are on the top of the head clearly behind the eyes. The nostrils, the mouth and the five gill slits are located on the underside of the head. The nostrils are short and wide. They are clearly separated from the mouth and are partially covered by large nasal curtains. The mouth is almost straight. The two dorsal fins are relatively large and far apart. The shape of both fins is similar, the first is only slightly larger than the second. The rear edge of the dorsal fins is concave. The attachment of the first dorsal fins lies clearly in front of the base of the pelvic fin. The pectoral fins are clearly set off from the head and trunk and are triangular. Your rear edge is straight. The pelvic fins are small and triangular. The caudal fin is well developed with a large upper and a small lower lobe.
Spread and endangerment
The common sawfish originally had a global tropical distribution and occurred with four subpopulations in the eastern and western Atlantic, in the eastern Pacific and in the Indo-Pacific , between 45 ° north and 17 ° south latitude, always near the coasts and the substrate. In the last few decades the number of animals in all four subpopulations has decreased dramatically and in many areas that originally belonged to the distribution area, the sawfish have now disappeared. In the western Atlantic, where the common sawfish originally came from Florida and Louisiana to Brazil , there may still be some animals in remote coastal areas of French Guiana, Suriname and Guyana, as well as freshwater stocks in the lower Amazon basin and in the catchment area of Rio San Juan and Lake Nicaragua in Nicaragua. From the eastern Atlantic, where the sawmill range from Portugal to Angola, there have been very few sightings of individual specimens in West African rivers, in the Ogooué and in the mouth of the Congo . The common sawfish has been extinct in the Mediterranean since the 19th century. A remaining distribution center of the species is the north coast of Australia. The common sawfish is listed as critically endangered by the IUCN.
Way of life
Common sawfish are euryhaline and also tolerate brackish and fresh water and inhabit the sandy or muddy bottom of shallow coastal waters, lagoons or estuaries as well as rivers and freshwater lakes. In rivers, the fish prefer cloudy, muddy areas. They hike up to 750 km up the Amazon . A population in Lake Nicaragua may be stationary, do not migrate and also reproduce in freshwater. Sawfish feed on fish and various bottom-dwelling invertebrates. The maximum age, determined from the growth rings of the vertebrae, is 51 years.
Reproduction
Common sawfish grow slowly, mature late, reproduce ovoviviparously, and have low fertility. In Lake Nicaragua, where there is a stationary, non-migratory population that also reproduces there, the fish likely mate from May to July and the fry are born about five months later from October to December. One to 13 young fish are born per litter, which are around 73 to 80 cm long at birth. In their first year of life they grow 35 to 40 cm. As they get older, their growth rate decreases more and more and is 12 cm at the age of ten and up to 4 to 5 cm per year in the last ten years of their life. They become sexually mature at the age of ten years with a length of about three meters. On the coasts of western Australia, the fish are said to be 80 to 90 cm long shortly after birth and the population in the Indo-Pacific is expected to reach sexual maturity with a length of 2.4 meters. In Queensland , the fry are born in freshwater, spend the first three to four years in freshwater, growing up to two meters in size, and later migrate to the estuaries and coastal marine areas. Specimens have been found 325 km upstream in the Mitchell River and 500 km upstream in the Einasleigh River , and 300 km upstream in the Fitzroy River , northwest Australia . The sawfish found in New Guinea also spawn in fresh water. They are found relatively often in the large rivers Fly , Sepik , Ramu , Mamberamo and Digul . They are particularly common in the middle Fly River, or in the Lake Murray connected to it , where they inhabit the main arms and oxbow lakes. Individual animals have been sighted as far as the upper reaches in the area around Kiunga .
Systematics and taxonomy
Carl von Linné described the common sawfish in his Systema Naturae in 1758 under the name Squalus pristis as "a shark with a flat, bony, sword-like snout, toothed on both sides". He relied on older descriptions by the French naturalist Guillaume Rondelet from 1554 and the Flemish-Dutch scholar Charles de l'Écluse (Clusius) from 1605. The genus Pristis was introduced in 1790 by the German natural scientist Heinrich Friedrich Link .
Synonyms of Pristis pristis are Pristis antiquorum Latham, 1794 Pristis canaliculata Bloch & Schneider, 1801 Pristis leichhardti Whitley, 1945 Pristis microdon Latham, 1794 Pristis perotteti Müller & Henle 1841 and Pristis zephyreus Jordan 1895. microdon Pristis and Pristis perotteti were still until 2012 as an independent species and were combined with Pristis pristis to form the Largetooth Group within the sawfish. The synonymization took place after no morphological differences were found between specimens of the three species deposited in museums . In the genus Pristis is Pristis pristis basal sister group to another of the three types ( dwarf sawfish ( P. clavata ), narrow tooth Sägerochen ( P. pectinata ) u. Long comb Sägerochen ( P. zijsron formed)) clade .
Individual evidence
- ↑ a b c d e Vicente V. Faria, Matthew T. McDavitt, Patricia Charvet, Tonya R. Wiley, Colin A. Simpfendorfer & Gavin JP Naylor: Species delineation and global population structure of Critically Endangered sawfishes (Pristidae). Zoological Journal of the Linnean Society, Vol 167, Issue 1, 2012, DOI: 10.1111 / j.1096-3642.2012.00872.x
- ↑ Kyne, PM, Carlson, J. & Smith, K. Pristis pristis . In: IUCN 2013. 2013 IUCN Red List of Threatened Species. At www.iucnredlist.org . Accessed March 21, 2020.
- ↑ Common sawfish on Fishbase.org (English)
- ↑ G. Allen, S. Midgley, M. Allen: Field Guide to the Freshwater Fishes of Australia . 2nd Edition. Western Australian Museum, Perth 2003, ISBN 0-7307-5486-3 .
- ↑ GR Allen, AW Storey, M. Yarrao: Freshwater Fishes of the Fly River . Ok Tedi Mining, Tabubil 2008, ISBN 978-0-646-49605-4 .
- ↑ Pristis in the Catalog of Fishes (English)
