Great pike
| Great pike | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Great nil pike ( Gymnarchus niloticus ) |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Gymnarchidae | ||||||||||||
| Bleeker , 1859 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Gymnarchus | ||||||||||||
| Cuvier , 1829 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Gymnarchus niloticus | ||||||||||||
| Cuvier , 1829 |
The gymnarchus ( Gymnarchus niloticus ) is a large African freshwater fish from the order of Knochenzünglerartigen (Osteoglossiformes).
distribution
Gymnarchus niloticus comes between the 5th and the 18th northern Africa Latitude in the Nile , Niger , Volta , Lake Chad , Senegal , Gambia Basin and Lake Rudolf in front. The species is not threatened by humans (no documented overfishing ), although gymnarchids are traded as food fish in some regions.
features
The Greater Nile Pike resembles an upside-down knife fish and has a spindle-shaped body with a blackish-gray top and a light belly. On average, the fish reach a length of 90 centimeters, a maximum of 1.67 meters in length and a weight of 18.5 kg are documented. The long dorsal fin, supported by 183 to 230 fin rays, extends from the head end over a large part of the body and ends on the tapering caudal fin stalk. The amiiform , wave-like movements of this fin edge allow the fish to move very skillfully both forwards and backwards while keeping their bodies stiff. When swimming backwards, the tip of the tail serves as a tactile organ. A caudal fin is missing, as are the anal fin and the pelvic fins. The pectoral fins are relatively small. The tongue and parasphenoid are toothless. There are four Branchiostegal rays . The scales are small, the head is scaly.
Active electrical location and communication
Large pike have the ability to electrical communication and electrical orientation . The electrical organ consists of four columns of electrocyths, is located in the rear third of the body and extends to the tip of the tail. This continuously generates electrical impulses which, at a temperature of 21 to 31 ° C, have a frequency of 50 to 60 Hertz . A voltage of 3 V was measured in large specimens . Great pike also have electroreceptors to perceive electrical voltages.
Way of life
Great Nile pike live in the thickets of aquatic plants on the banks of the river bank and in swamps and feed on crustaceans, insects and, above all, fish. At high tide they leave the river bed and migrate to the floodplain . To reproduce, they build elliptical swimming nests from plant material in which the female lays around 1000 amber-colored eggs one centimeter in diameter. The hatching larvae have a large yolk sac and external thread gills.
Systematics
The greater Nilhecht forms a monotypical family within the Osteoglossiformes , the Gymnarchidae. Together with the Nilhechten (Mormyridae) it forms the superfamily Mormyroidea, but differs from the Nilhechten in its non-enlarged cerebellum.
literature
- Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish , Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00339-6
- Joseph S. Nelson : Fishes of the World , John Wiley & Sons, 2006, ISBN 0-471-25031-7
Web links
- Greater Nilhecht on Fishbase.org (English)
- Gymnarchus niloticus inthe IUCN 2013 Red List of Threatened Species . Posted by: Azeroual, A., Entsua-Mensah, M., Getahun, A., Lalèyè, P., Moelants, T. & Vreven, E., 2009. Retrieved January 12, 2014.