Tette, Sena, Quellimane, Lumbo, Inhambane, and Querimba, Mozambique (Peters 1852).
Etymology/Derivation of Scientific Name
Oreochromis – Greek oreos, “of the mountains” and chroma, “color” (Boschung and Mayden 2004); mossambica describes the geographic area, Mozambique, to which the species is native (Jubb 1967; Moyle 1976).
Trewavas (1983) uses the genus name Oreochromis for this tilapiine fish formerly in Tilapia; see also for additional synonyms and notes on the synonyms.
Chromis mossambicus Peters 1852:681.
Maximum size: 360 mm SL (Hensley and Courtenay 1980).
Coloration: Hubbs et al. (1991) listed the following for this species in Texas waters: sides with 3 or 4 dark blotches or with no markings; no yellow on dorsal fin; caudal fin without distinct vertical lines. Coloration is gray to olive above; dull yellow to gray-green on side; yellow below (Page and Burr 1991). In life, genital papilla chalky white (Boschung and Mayden 2004). Young has 6-8 black bars on side (Page and Burr 1991). Breeding males mostly black, often with mottling or an iridescent blue tinge; throat and cheeks conspicuously white; dorsal fin black with red border; caudal fin with red distal border; pectoral fins red (Boschung and Mayden 2004); with blue upper lip (Moyle 1976; Page and Burr 1991).
Counts: 14-20 (usually 17-18) gill rakers on lower part of first gill arch; fewer than 5 anal fin spines (usually 3; Hubbs et al. 1991); 29-33 in lateral series, in 2 to 3 rows on the cheek below the eye (Moyle 1976); 15-16 dorsal fin spines; 10-12 dorsal fin rays; 3-4 anal fin spines; 9-10 anal fin rays; 14-15 rays on each pectoral fin (Boschung and Mayden 2004).
Body shape: Deep, compressed body is typical of the family Cichlidae (Boschung and Mayden 2004). Snout bluntly pointed (Moyle 1976). Sexual dimorphism in frontal profile and mouth size (Hensley and Courtenay 1980); spawning males have enlarged mouths and thickened upper lips (Moyle 1976).
Mouth position: Large oblique mouth reaches under front of eye or beyond (Page and Burr 1991).
External morphology: Scales cycloid; caudal fin rounded; gill rakers short (Moyle 1976).
Internal morphology: Most teeth in outer row are unicuspid in adults (Hubbs et al. 1991); intestine long and coiled (Moyle 1976).
Distribution (Native and Introduced)
U.S. distribution: Established in California, Arizona, Texas, Florida, and North Carolina; possibly established in Georgia and Colorado; has been collected in Montana, and New York and is stocked annually in ponds and lakes in Alabama; established in estuarine and possibly marine waters in California (Hensley and Courtenay 1980).
Texas distribution: Native to Africa, this aquaculture species has been introduced into the state and has become established primarily in the San Marcos, Guadalupe, and San Antonio Rivers along the Balcones fault zone (Hubbs et al. 1991). Species first reported from the San Antonio River in the late 1950’s, as a result of fish escaping from the channel running through the San Antonio Zoo (Brown 1961; Edwards 2001). In the upper San Antonio River, Texas, species captured abundantly in the upper site in nearly all habitats sampled; in terms of biomass, this species dominated all others at this site; number of individuals captured in this sample was markedly larger than the small number taken in the earlier 1977 collection by Hubbs et al. (1978; Edwards 2001). One specimen collected from Santa Isabel Creek (Rio Grande drainage) at Farm Road 1472 crossing (Webb Co.) on 13 February 1990 (Platania 1990).
Abundance/Conservation status (Federal, State, NGO)
Species is abundant at some United States localities (Hensley and Courtenay 1980).
Macrohabitat: Species able to live and reproduce in fresh water and sea water (Hensley and Courtenay 1980). The preferred habitat seems to be warm, weedy ponds, canals and backwaters of rivers (Moyle 1976).
Mesohabitat: Prefers slow or still, weedy waters; can tolerate temperatures of 12 degrees C in fresh water and at least as low as 11 degrees C in saline water (Hensley and Courtenay 1980); able to survive temperatures as low as 5ºC and as high as 43ºC for short periods of time (Moyle 1976); the normal living range is about 11ºC - 38ºC, with optimum growth at about 30ºC (St. Amant 1966; Moyle 1976). In the upper San Antonio River, Texas, species was readily collected in slow moving water and habitats broken into run, riffle, and glide regimes; also displayed apparent preference for stream reaches with rocky bottoms; collected in the back water, mud bottom habitat in Picosa Creek; this species is pollution tolerant, but also temperature sensitive and fish kills are common in shallow areas when air temperature remains below freezing for extended periods (Gonzales and Moran 2005). In the upper San Antonio River, Texas, largest adults observed defending redds in the main channel, as well as the side channel leading from the San Antonio Zoo (Edwards 2001). In the lower Colorado River, species abundant mostly in areas influenced by warm, salty irrigation water (E. McClendon, pers. comm. in: Moyle 1976).
Spawning season: Species will breed continually as long as the temperature remains above 20ºC (Moyle 1976).
Spawning habitat: After establishing a territory in a shallow, weedy area, the male will clear an area about 30 cm in diameter of weeds and dig a shallow pit over which the eggs will later be released by the female and fertilized by the male (Moyle 1976; Boschung and Mayden 2004). Capable of breeding in sea water (Brock and Takata 1954; Jubb 1967; Moyle 1976).
Spawning Behavior: Maternal mouth-brooders, carrying fertilized eggs in the mouth (Hensley and Courtenay 1980). Male leaves the school of non-breeding fish to establish a territory, after which the male will remain active, digging, courting spawning, feeding and fighting with neighboring fish. Male begins courtship with a display in front of a group of females. A willing female will then follow the male to his territory where the pair will circle, with the female occasionally biting at the bottom. While circling, female releases numerous eggs, then turns and collects them in her mouth, as well as the milt deposited by the male; thus fertilizing the eggs. This act is repeated until 100-400 eggs are laid, the number depending on size of the female. Once spawning is complete the female is chased out of the territory by the male, who proceeds to court other females. For the next 11-12 days, the female will incubate the eggs while remaining hidden. At the end of the incubation period, the female releases the swimming larvae from her mouth. For 4-8 days, the young remain near the female in a school, and will return to her mouth or cluster around her head when threatened (Moyle 1976; Boschung and Mayden 2004).
Fecundity: Female with deposit from 100 to 400 eggs during spawning period, the number depending on size of female (Moyle 1976; Boschung and Mayden 2004). In Brisbane, Australia mean fecundity was 1360 (±117.2 standard error) in North Pine Dam and 2107 (±220.4 standard error) in Tingalpa Reservoir; oocyte diameter ranged from 1.7-2.6 mm (Arthington and Milton 1986).
Age/Size at maturation: Ordinarily less than 6 months after hatching, at lengths of 120 to 140 mm TL (Moyle 1976; Trewavas 1983; Boschung and Mayden 2004). Maturation of fish from two Brisbane, Australia reservoirs was at 12-15 months, at minimum sizes of 152 mm SL in males and 174 mm SL in females (Arthington and Milton 1986).
Migration: Arthington and Milton (1986) reported that pre-reproductive and mature females occupied shallow littoral areas in warmer months of September - April, and suggested that their failure to collect the species in the littoral from May – August, in spite of identical methodology may have been due to movement of fish into deeper water or open water, as similar seasonal movements by this species have been reported from Lake Sibaya, South Africa.
Growth and Population Structure: Males grow faster than females (Fryer and Iles 1972; Moyle 1976; Trewavas 1983); Arthington and Milton (1986) observed male predominance only among fish larger than 200 mm SL. In South African ponds, fish attained lengths of 82-101 mm TL in their first year, 118-182 mm, 140-253 mm, 165-296 mm, 195-323 mm, 227-348 mm, 245-377 mm, 259 mm, and 269 mm TL at ages 2-9, respectively (Fryer and Illes 1972; Boschung and Mayden 2004).
Longevity: Maximum age is about 11 years (Fryer and Iles 1972; Moyle 1976; Boschung and Mayden 2004).
Food habits: Omnivorous (Henley and Courtenay 1980; Gonzales and Moran 2005). Long coiled intestine and feeding habits suggest the species is largely herbivorous, consuming planktonic algae and aquatic plants. However, species lacks the enzyme cellulase, needed to digest cellulose; consequently much ingested plant material must pass through the gut undissolved. Diet items include adult and larval aquatic insects and isopods; small fish are consumed also (Moyle 1976; Boschung and Mayden 2004). Species placed in the opportunistic omnivore category by Boschung and Mayden (2004).
Phylogeny and morphologically similar fishes
Oreochromis mossambicus is similar to O. aureus (blue tilapia), but O. aureus has usually 12-15 dorsal fin rays, 18-26 rakers on the lower limb of 1st gill arch, and the large male has a blue-black chin and breast (Page and Burr 1991).
Nemata: Rhabdochona (from Texas; Underwood and Dronen, Jr. 1984), and Spiroxys contorta (from Texas; Mayberry et al. 2000).
Commercial or Environmental Importance
Introductions of this species into U.S. are due to intentional releases by government agencies and aquarists and escapes from government hatcheries, private fish farms, and a public aquarium (Hensley and Courtenay 1980). The release of this exotic species is undesirable and strongly discouraged (Moyle 1976; Boschung and Mayden 2004). According to Shelton and Smitherman (1984), Oreochromis mossambicus is cultured in many areas world-wide, but the species is less desirable than other tilapia fishes due to its earlier maturity and consequent greater tendency to overpopulate.
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Brock, V. E. and M. Takata. 1952. A note on spawning of Tilapia mossambica in seawater. Copeia 1954(1):72.
Brown, W.H. 1961. First record of the African mouthbreeder Tilapia mossambica Peters in Texas. Texas J. Sci. 13:352-354.
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Fryer, G. and T. D. Illes. 1972. The Cichlid Fishes of the Great Lakes of Africa: Their Biology and Evolution. Oliver and Boyd, Edinburgh. 641 pp.
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Mayberry, L.F., A.G. Canaris, J.R. Bristol, and Scott L. Gardner. 2000. Bibliography of parasites and vertebrate host in Arizona, New Mexico and Texas (1893-1984). University of Nebraska Harold W. Manter Laboratory of Parasitology Web Server, published on the World-Wide-Web, 100 pp.
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Peters, W.C.H. 1852. Diagnosen von neuen Flussfuschen aus Mossambique. Monatsberichte der Koniglichen Preussiche Akademic des Wissenschaften zu Berlin 1852:681-685.
Platania, S.P. 1990. The ichthyofauna of the Rio Grande drainage, Texas and Mexico, from Boquillas to San Ygnacio. Report to U.S. Fish and Wildlife Service, Arlington, Texas. 100 pp.
Shelton, W.L., and R.O. Smitherman. 1984. Exotic fishes in warmwater aquaculture. Pp. 262-301 in: W.R. Coutenay, and J.R. Stauffer (eds.). Distribution, Biology, and Management of Exotic Fishes. Johns Hopkins University Press, Baltimore.
St. Amant, J.A. 1966. Progress report of the culture of Tilapia mossambica (Peters) hybrids in southern California. Resources Agency of California Department of Fish and Game, Inland Fisheries Administrative Report 66-9:25.
Trewavas, E. 1983. Tilapiine Fishes of the Genera Sarotherodon, Oreochromis and Danakila. British Museum (Natural History) Publ. No. 898. 593 pp.
Underwood, H.T., and N.O. Dronen, Jr. 1984. Endohelminths of fishes from the upper San Marcos River, Texas. The Southwestern Naturalist 29(4):377-385.