Picture by Chad Thomas, Texas State University-San Marcos
West Africa (Steindachner 1864).
Etymology/Derivation of Scientific Name
Oreochromis, Greek oreos, “of the mountains” and chroma, “color;” aureus, Latin, meaning “golden,” from aurum, “gold” (Boschung and Mayden 2004).
Chromis aureus Steindachner 1864:229.
Tilapia aurea Hubbs et al. 1991:48-49.
Maximum size: 508 mm TL (Hensley and Courteney 1980).
Coloration: Sides unmarked or with vague, irregular dark markings; caudal fin often with a broad, red distal margin; young often with vertical bands on caudal fin (Hubbs et al 1991). In adults, side bluish gray, white on belly, except in darker individuals each scale bearing small dark spot forming stripes (Boschung and Mayden 2004). Large male has bright metallic blue head, pale blue side, blue-black chin and breast (Page and Burr 1991). Breeding males usually bluish gray, throat and cheeks somewhat lighter than rest of body. In life, genital papilla translucent, not chalky white (Boschung and Mayden 2004).
Counts: 18-26 gill rakers on lower part of first gill arch; fewer than 5 anal spines (usually 3; Hubbs et al. 1991); usually 12-15 dorsal rays (Page and Burr 1991); total gill rakers 24-32, usually more than 26; lateral scale rows 30-33; dorsal fin spines usually 15 or 16; anal fin rays 9-11 (Boschung and Mayden 2004).
Body shape: Deep, compressed (Boshung and Mayden 2004).
Mouth position: Oblique (Page and Burr 1991).
External morphology: Single naris on each side of head; interrupted lateral line; caudal fin truncate. During periods of sexual activity, margin of dorsal fin of male thickens and its outline becomes continuous instead of notched (Boschung and Mayden 2004).
Internal morphology: Outer row of teeth bicuspid in adults (Hubbs et al. 1991).
Distribution (Native and Introduced)
U.S. distribution: Established in Texas and Florida; previously established population in Oklahoma probably no longer extant; possibly established in Arizona, Georgia, and Colorado; annually stacked in ponds and lakes in Alabama; introduced in North Carolina but did not survive (Hensley and Courtenay 1980). Native to the Middle East and along the Mediterranean Coast of North Africa (Hubbs et al. 1991).
Texas distribution: Aquacultural species has been introduced into state and has become established in the Rio Grande, San Antonio, Guadalupe, and parts of the Colorado River drainages (Hubbs et al 1991). Breeding population present in San Felipe Creek, Texas (Lopez-Fernandez and Winemiller 2005).
Abundance/Conservation status (Federal, State, NGO)
Abundant in United States localities (Hensley and Courtenay 1980); common (Page and Burr 1991).
Macrohabitat: Warm ponds and impoundments (Page and Burr 1991).
Mesohabitat: In Texas, most successful establishments are in areas without extremely cold winter water temperatures (examples include the lower Rio Grande Basin and reservoirs heated by power plant effluents) (Hubbs et al 1991). Able to live and reproduce in fresh and brackish water; established in brackish water in Tampa Bay, Florida. Lower temperature tolerance about 13 degrees C (Hensley and Courtenay 1980). Dolman (1990) reported that this species was consistently associated with Dorosoma petenense (threadfin shad) in a group of Texas reservoirs. Edwards and Contreras-Balderas (1991) found species to be dominant perciform (often dominant taxon) in collections taken upstream from the Brownsville, Texas and Matamoros, Tamaulipas area; appeared to be colonize habitats in more generalized fashion than nearly any other species found in the stream system; Oreochromis aureus increasing in abundance in this region despite massive reduction in numbers during a winter die-off in late 1983 (Wood 1986; Edwards and Contreras-Balderas 1991).
Spawning habitat: In both fresh and brackish water (Hensley and Courtenay 1980).
Spawning behavior: Maternal mouthbrooder (Hensley and Courtenay 1980).
Fecundity: Ripe ovaries of a female 250 mm TL may contain about 4300 eggs; however, more eggs mature in the ovaries than are laid. 1300 embryos were reported from the mouth of a specimen from Lake Tiberias (Fryer and Iles 1972; Boschung and Mayden 2004).
Age at maturation: At 2 years, when individuals are usually 180-200 mm TL (Boschung and Mayden 2004).
Growth and Population structure: Exhibits male growth superiority (Hensley and Courtenay 1980). In Africa, average growth in ponds at ages 1-5 is 102, 190, 240, 275, and 290 mm TL, respectively (Fryer and Iles 1972; Boschung and Mayden 2004).
Longevity: 5+ years (Boschung and Mayden 2004).
Food habits: Omnivore/detritivore (Gu et al. 1997). Feeds primarily on photoplankton (Hensley and Courtenay 1980). In lower Rio Grande River, Texas, food habits extremely generalized (Wood 1986; Edwards and Contreras-Balderas 1991). In Lake Farfield, Texas, species consumed vegetable matter, detritus, and chironomid larvae (Traxler and Murphy 1995).
Phylogeny and morphologically similar fishes
Similar to Oreochromis mossambicus, the Mozambique tilapia, but has usually 12-15 dorsal rays, and 18-26 rakers on lower limb of 1st gill arch (Page and Burr 1991). O. aureus superficially resembles species of sunfishes (Lepomis) but is readily distinguished by having an uninterrupted lateral line and a single naris versus uninterrupted lateral line and double nares (Boschung and Mayden 2004). Oreochromis aureus X Oreochromis mossambicus (Mozambique tilapia) hybrids reported from central Texas (Howells 1991).
Bacteria: Flexibacter columnaris; Protozoa: Apiosoma piscicolum, Epistylis colisarum, Trichodina sp., Trypanoplasma sp.; Monogenea: Cichlidogyrus tilapiae, Gyrodactylus cichlidarum, Neobedenia melleni (Bunkley-Williams and Williams 1994).
Commercial or Environmental Importance
Introductions into United States due to intentional releases by government agencies, escapes from fish farms, and intentional releases into power plant cooling reservoirs (Hensley and Courtenay 1980). Boschung and Mayden (2004) note that the species is an undesirable exotic and discourage its release into the wild. Species regarded as nuisance due to threat posed to native species (Cole 2006).
[Additional literature noting collection of this species from Texas locations includes, but is not limited to the following: Fairfield Reservoir (Freestone Co.; Ippolito 1985); Trinidad Lake (Noble and Germany 1986); Starling (1986); Winemiller et al. (2000); Edwards (2001).]
Boschung, H. T., Jr., and R. L. Mayden. 2004. Fishes of Alabama. Smithsonian Books, Washington, D.C. 736 pp.
Bunkley-Williams, L., and E.H. Williams, Jr. 1994. Parasites of Puerto Rican Freshwater Sport Fishes. Puerto Rico Department of Natural and Environmental Resources, San Juan, PR and Department of Marine Sciences, University of Puerto Rico, Mayaguez, PR. 168 pp.
Cole, R.A. 2006. Freshwater aquatic nuisance species impacts and management costs and benefits at Federal Water resources projects. ANSRP Technical Notes Collection (ERDC/TN ANSRP-06-3), U.S. Army Engineer Research and Development Center, Vicksburg, MS. 14 pp.
Dolman, W.B. 1990. Classification of Texas reservoirs in relation to limnology and fish community associations. Trans. Amer. Fish. Soc. 119:511-520.
Edwards, R.J. 2001. Ecological profiles for selected stream-dwelling Texas freshwater fishes III. Report to the Texas Water Development Board. 59 pp.
Edwards, R.J., and S. Contreras-Balderas. 1991. Historical changes in the ichthyofauna of the lower Rio Grande (Rio del Norte), Texas and Mexico. 36(2):201-212.
Fryer, G., and T.D. Iles. 1972. The Cichlid Fishes of the Great Lakes of Africa: Their Biology and Evolution. Oliver and Boyd, Edinburgh. 641 pp.
Gu, B., C.L. Schelske, and M.V. Hoyer. 1997. Intrapopulation feeding diversity in blue tilapia: evidence from stable isotope analysis. Ecology 78:2263-2266.
Hensley, D.A., and W.R. Courtenay, Jr. 1980. Tilapia aurea (Steindachner), Blue tilapia. pp. 771 in D. S. Lee, et al. Atlas of North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raliegh. 854 pp.
Howells, R.G. 1991. Electrophoretic identification of feral and domestic tilapia in Texas. Texas Parks and Wildlife Dept., Manage. Data Ser. 62:1-11.
Hubbs, C., R. J. Edwards, G. P. Garrett. 1991. An annotated checklist of freshwater fishes of Texas, with keys to identification of species. The Texas Journal of Science, Supplement 43(4):1-56.
Ippolito, D.F. 1985. A winter die off in Fairfield Reservoir (Freestone County, Texas), with special emphasis on mortality in Sarotherodon aureus (Cichlidae). The Southwestern Naturalist 30(3):456-459.
Lopez-Fernandez, H., and K.O. Winemiller. 2005. Status of Dionda diaboli and report of established populations of exotic fish species in lower San Felipe Creek, Val Verde County, Texas. Southwestern Naturalist 50(2):246-251.
Noble, R. L., and R.D. Germany. 1986. Changes in fish populations of Trinidad Lake, Texas, in response to abundance of blue tilapia. pp. 455-461 in R.H. Stroud, ed. Fish Culture in Fisheries Management. American Fisheries Society, Fish Culture Section and Fisheries Management Section, Bethesda, Maryland.
Page, L.M., and B. M. Burr. 1991. A Field Guide to Freshwater Fishes of North America, north of Mexico. Houghton Mifflin Company, Boston. 432 pp.
Starling, S.M. 1986. Effects of a reduction of blue tilapia, Oreochromis aureus, on the ichthyofauna of a power-plant reservoir. M.S. Thesis, Texas A&M University. College Station.
Steindachner, F. 1864. Ichthyologische Mittheilungen. VII. Verh. K. K. Zool.-Bot. Ges. Wein 14:223-232.
Traxler, S.L., and B. Murphy. 1995. Experimental trophic ecology of juvenile largemouth bass, Micropterus salmoides, and blue tilapia, Oreochromis aureus. Environmental Biology of Fishes 42(2):201-211.
Winemiller, K.O., S. Tarim, D. Shormann, and J.B. Cotner. 2000. Fish assemblage structure in relation to environmental variation among Brazos River oxbow lakes. Trans. Amer. Fish. Soc. 129:451-468.
Wood, M.G. 1986. Life history characteristics of introduced blue tilapia, Oreochromis aureus, in the lower Rio Grande, Texas. M.S. Thesis, The University of Texas - Pan American, Edinburg. 91 pp.