**4. Presentation of the species** *O. niloticus* **(Linneaus, 1758)**

Like all tilapias, *O. niloticus is a* member of the family Cichlidae (**Figure 1**). The systematic position adopted for this species is the following [1, 9] Phylum: Vertebrates; Subphylum: Gnathostomes; Superclass: Fishes; Class: Osteichthyes; Subclass: Teleosts; Order: Perciformes; Suborder: Percoids; Family: Cichlidae; Subfamily: Tilapinae; Genus: *Oreochromis*; Species: *niloticus*.

#### **4.1 Morphological characteristics of the species**

Nile tilapia is a Cichlid belonging to the group of maternal mouth-brooder fish. It is characterized by a grayish coloration with pinkish breast and flanks, alternating light, black vertical stripes clearly visible especially on the caudal fin and the posterior part of the dorsal fin, a high number of long and thin gill rakers (18–28 on the lower part of the first gill arch and 4–7 on the upper part), a long dorsal fin with a spiny anterior

**Figure 1.** *Nile tilapia (present work).*

part (17–18 spines) and a soft posterior part (12–14 rays), and a black border on the dorsal and caudal fin in males [24–26]. *Oreochromis niloticus* can be easily distinguished from any other species of tilapia that has more or less the same characteristics mentioned above, i.e., *O. aureus*, but which shows in males an additional red border along the edge of the dorsal and caudal fins [27, 28].
