Oreochromis niloticus
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Oreochromis niloticus |
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| Scientific name | ||||||||||||
| Oreochromis niloticus | ||||||||||||
| ( Linnaeus , 1758) |
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Oreochromis niloticus or Nile cichlid is a species of fish from the cichlid family (Cichlidae), which isvery widespreadwith eight subspecies in West , Northeast and East Africa and alsooccursin the Middle East .
features
Oreochromis niloticus can grow to be around 60 cm long and weigh over 4 kg. He has a very high back and laterally flattened body, which is covered with cycloid scales. The body height is 40 to 47% of the standard length , the head length 31.5 to 40.5% of the standard length and the lower jaw length 29 to 37% of the head length. The jaws of smaller fish have 3 to 4 rows of teeth, larger specimens (longer than 20 cm) have 4 to 6 rows of teeth. The teeth of the outer row of teeth are two-pointed. The lower pharyngealia is as wide as it is long, or slightly wider. Its ventral keel is longer than the triangular, toothed area. On the lower branch of the first gill arch there are 18 to 28 gill trap rays .
- Fins formula : dorsal XV – XVIII / 11–13, anal III / 9–11.
- Scale formula : SL 31–34, 2–3 rows of scales on the sides of the head.
- Vertebra: 30-32.
The most striking characteristic of Oreochromis niloticus are the vertical stripes on the caudal fin. Otherwise the fish are of a gray basic color and show 6 to 9 vertical, olive-green stripes on the sides of the body. The belly is whitish, the upper lip green or white, the lower lip white. Dorsal and anal fins are greyish, sometimes with a narrow reddish border. The pectoral fins are transparent, the pelvic fins are gray. During the breeding season, the males show a reddish tinge on the head, body, dorsal and caudal fin.
Way of life
Oreochromis niloticus occurs in many different freshwater habitats and has a high temperature tolerance (13.5–33 ° C). These can be rivers, lakes or irrigation canals. It feeds mainly on phytoplankton and algae. Like all Oreochromis species, Oreochromis niloticus is also a mouthbrooder in which the breeding business is only carried out by the female.
Subspecies
- Oreochromis niloticus baringoensis Trewavas , 1983; Baringo Lake ( Kenya ).
- Oreochromis niloticus cancellatus (Nichols, 1923); Lakes of the Ethiopian Rift Valley , Lake Basaka and Awash system, but not in Lake Tana and Lake Turkana .
- Oreochromis niloticus eduardianus (Boulenger, 1912); Albert Nile , Albert , Edward , Georg , Kivu , Ruzizi and Tanganyika lakes . (Introduced in Lake Victoria and Lake Kyoga and in many other small lakes and reservoirs in Uganda and Rwanda ).
- Oreochromis niloticus filoa Trewavas, 1983; Awash system without Lake Basaka; possibly also in Akaki Lake.
- Oreochromis niloticus niloticus (Linnaeus, 1758); Israel , river basin of the Nile from Albertnil to the Delta, West Africa ( Senegal , Gambia , Volta , Niger and Benue ) and in Lake Chad . In numerous countries the subspecies was introduced as a food fish.
- Oreochromis niloticus sugutae Trewavas, 1983; Northwest Kenya, also in thermal springs .
- Oreochromis niloticus tana Seyoum & Kornfield, 1992; Lake Tana (highlands of Ethiopia).
- Oreochromis niloticus vulcani (Trewavas, 1933); Lake Turkana (Kenya) and tributaries with the exception of the Omo .
Use in aquaculture
The undemanding Nile cichlid is one of the most important food fish species for global aquaculture. It is now one of the most popular types of use in the USA too. In 2017, the annual production according to FAO was 4,130,281 tons. At a water temperature between 20 to 35 ° C, the omnivorous tilapia species can grow up to 60 centimeters. The Nile cichlid feeds on detritus , algae growth (periphyton), biofilm, small crustaceans, invertebrates and aquatic plants. Under certain conditions, it can even absorb the finest nutrient particles from the water. It can also be fattened to a certain degree with feed that contains a low protein content. For the production of one kilogram of tilapia meat, about 0.7 kg of feed fish meat are necessary. He has an excellent feed conversion coefficient . It is particularly suitable for aquaculture because of its firm and tasty meat, ease of reproduction, particularly rapid growth and resistance to pathogens. As a result of its mouth-brooding behavior, the failure and loss rates in the Nile cichlid are significantly lower than in other fish species. The most important producing countries are currently Egypt , China and Indonesia . But smaller countries like Honduras have also started producing tilapias. The production takes place in several stages: the spawning process of the parent stock and the brood care by the female animals. Furthermore, by rearing larvae in ponds or tanks. Sex reversal is carried out in the larvae. Then the animals come to the fattening. This can take place in closed circulation systems, open flow systems, net cages, semi-intensively used ponds or extensively used ponds. After five to six months, the Nile cichlids are ready for slaughter.
literature
- Melanie Stiassny, Guy Teugels & Carl D. Hopkins: The Fresh and Brackish Water Fishes of Lower Guinea, West-Central Africa. Volume 1, ISBN 978-90-74752-20-6
Individual evidence
- ↑ a b c d e f g h Tilapia (Oreochromis niloticus) on www.aquakulturinfo.de
- ↑ The tilapia is one of the most popular types of fish in the USA, but we still have difficulties getting started. In fact, tilapia is not without controversy. Tilapia. Eat smarter. December 27, 2018
- ↑ Tilapia. Oreochromis ssp.
- ↑ Tilapia - Resistant even under difficult growing conditions. alimentarium
- ^ Tilapia Hondureña
- ↑ Ronald P. Phelps and Thomas J. Popma: Sex reversal of Tilapia. Tilapia Aquaculture in the Americas. Vol. 2, The World Aquaculture Society. 2000
Web links
- Oreochromis niloticus on Fishbase.org (English)