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Tuggurt, Algeria (Gervais 1848).
Etymology/Derivation of Scientific Name
Zillii. Patronym for M. Zill, a naturalist who provided Paul Gervcais with the type specimen (Boschung and Mayden 2004; Moyle 1976). Tilapia is derived from the native African (Bechuana) word thlape meaning fish. (Moyle 1976).
Maximum size: 320 mm (Daget 1956).
Coloration: The typical nonbreeding coloration is dark olive on the back and light olive or yellow brown on the sides. The sides often with an iridescent sheen and 6 to 7 poorly defined vertical bars. The belly is yellow to white and the fins are brown to yellow. The dorsal fin has a dark "eye-spot" on the soft-rayed portion, often outlined in yellow, along with numerous small yellow spots on the entire fin. The operculum also has a distinct dark spot. Spawning fish become shiny dark green on the back and sides with red and black on the throat and belly and distinct vertical bands on the sides. Their heads turn dark blue black, mottles with blue-green spots (Moyle 1976).
Pharyngeal teeth count:
Counts: The dorsal fin has 14 to 16 spines and 10 to 13 rays, rays being considerably longer than the spines. Anal fin has three to four spines, seven to ten rays; pectorals have 14 to 15 rays each. there are 28 to 30 cycloid scales in the lateral series (Moyle 1976).
Body shape: Typical cichlid body, elongate yet deep and laterally compressed, and the long dorsal fin (Moyle 1976).
Mouth position: Large, almost horizontal; jaw teeth with outer row incisor-like, inner row smaller and multicuspid. (Boschung and Mayden 2004)
External morphology: The 8 to 12 gill rakers are shorter than those of Mozambique mouthbrooders (Moyle 1976).
Additional from Hubbs key: Eight to ten gill rakers on lower part of first gill arch. Transverse bands present on sides, dorsal fin with yellow spots (Hubbs et al. 1991).
Distribution (Native and Introduced)
U.S. distribution: has been found in California, Florida, Arizona and annually stocked in farm ponds and lakes in Alabama (Hensley and Courtenay 1980).
Texas distribution: Introduced and has been established in the headwaters of the San Antonio River (Hubbs et al. 1991).
Abundance/Conservation status (Federal, State, NGO)
Macrohabitat: Normally inhabits large lakes and rivers but adapts well to ponds, ditches and other artificial habitats, especially where aquatic vegetation is abundant (Boschung and Mayden 2004).
Mesohabitat: It is a euryhaline species that can live and reproduce in waters with salinity as high as 45 ppt, and its lower lethal temperature is about 10ºC (Boschung and Mayden 2004).
Spawning season: Courtship and mate selection begins when the water warms to about 20ºC, In its native range and under optimal conditions of food and temperature, the species may breed throughout the year (Boschung and Mayden 2004).
Spawning habitat: In a constructed nesting depression much like that of sunfishes (Moyle 1976).
Spawning Behavior: Not a mouth-brooder; lays oblong eggs on substrate and parents guard eggs and young. (Hensley and Courtenay 1980) One or both members of the pair fan currents of water and pick debris and dead eggs from the nest (Boschung and Mayden 2004).
Fecundity: Lay between 1000 and 6000 eggs (Boschung and Mayden 2004).
Age at maturation: Two years (Daget 1956; Jensen 1957; Ben-Tuvia 1960, all cited in Fryer and Illes 1972).
Growth and Population Structure: grow to about 170 mm in first year and to about 315 mm in second year (Boschung and Mayden 2004).
Longevity: About six years (Daget 1956, cited in Fryer and Iles 1972).
Food habits: Omnivorous (Hensley and Courtenay 1980) young specimens are essentially carnivorous, eating small crustaceans; adults feed primarily on plants but also on some invertebrates, or dying/dead fish
(Boschung and Mayden 2004).
Phylogeny and morphologically similar fishes
Tilapia spp. have been found to have: Protozoa, Trematoda, Acanthocephala, Crustacea, Leech, Linguatula
Commercial or Environmental Importance
"The redbelly tilapia is an undesirable exotic, and we discourage its release into the wild." (Boschung and Mayden 2004).
They are being widely introduced into the warmer parts of the world for aquaculture and aquatic weed control, and they are actually efficient in controlling weeds in certain conditions. However, in low numbers they seem to be more selective over what they eat, therefore wild populations will most likely only change the plant composition rather than the plant density (Moyle 1976).
The species is a pollution tolerant omnivore, but is also temperature sensitive; fish kills are common in shallow areas when air temperature remains below freezing for extended periods. (Gonzales and Moran 2005). (Similar to the comment in O. mossambicus).
Ben-Tuvia, A. 1960. The biology of the cichlid fishes of Lakes Tiberias and Huleh. Bull. Res. Coun. Israel Sect. B. Zool., 8B:153-188.
Boschung, Herbert T. and Richard L Mayden. 2004. Redbelly Tilapia: Tilapia zillii (Gervais). pp622. in Fishes of Alabama. Smithsonian Books. Washington D.C. v-xviii+736.
Daget, J. 1956. Mémoires sur la biologie des poissons du Niger-Moyen. II. Recherches sur Tilapia zillii (Gervais). Bull. Inst. fr. Afr. noire 18, Ser. A., 165-223.
Fryer, G. and T. D. Illes. 1972. The Cichlid Fishes of the Great Lakes of Africa. TFH Publ., Hong Kong, 610 pp.
Gonzales, M. and E. Moran. 2005. An inventory of fish species within the San Antonio Missions National Historical Park. San Antonio River Authority, Final Report.
Hensley, D.A. and W.R. Courtenay, Jr. 1980. Tilapia zilli (Gervais) Redbelly tilapia pp. 775 in D.S. Lee et al. Atlas of North American Freshwater fishes. N.C. State Mus. Nat. Hist., Raleigh, i-r+854.
Hoffman, G. L. 1967. Parasites of North American Freshwater Fishes. University of California Pres. Berkeley and Los Angeles. vii-viii. 486 pp.
Hubbs, C. L., R. J. Edwards and G. P. Garrett. 1991. An annotated checklist of freshwater fishes of Texas, with key to identification of species. Texas Journal of Science, Supplement. 43(4):1-56.
Jensen, K. W. 1957. Determination of age and growth of Tilapia nilotica L., T. galilaea Art., T. zillii Gerv. and Lates niloticus C. et V. by means of their scales. K. norske Vidensk. Selsk. Forh., 30:150-157.
Moyle 1976 Inland fishes of California. University of California Press, Berkeley, California. pp 333.