Description
Synonomy- The American Fisheries Society prefers the name Tilapia aurea, but most references cited use the genus name Oreochromis (Courtenay et al. 1984: Page and Burr 1991), based on Trevawas' revision of the group.
Potentially Misidentified Species - A variety of Oreochromis, Sarotherodon, and Tilapia spp. from Africa and the Middle East are used for aquaculture and research. In addition, numerous African, Asian, and South American species of Cichlidae are kept as aquarium fish and are occasionally accidentally released in the Chesapeake drainage (Jenkins and Burkhead 1993). Some of these species are established in warmer parts of the United States (Courtenay et al. 1984). All are warm-stenothermic, and are unlikely to survive Chesapeake winters except possibly in the vicinity of thermal plumes.
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Chordata | Osteichthyes | Periciformes | Cichlidae | Oreochromis |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1984 | Extinct | Contracting | Introduced | Regular Resident | Africa | Africa | Fisheries(Fisheries Accidental) |
History of Spread
Oreochromis aureus (BlueTilapia) is native to 'the Senegal River, the middle Niger River...,pools and lagoons of the lower Chari and Logone rivers, the lower Nile from near Cairo to the Delta lakes...,the Jordan river system, the Na'aman and Yarkon rivers in Israel, and the Asraq rivers and hot pools at Ein Fashka, Jordan' (Courtenay et al. 1984). It was introduced to different parts of the U.S. for diverse purposes: to FL for weed control by 1962, with many separate introductions in warmer parts of United States, to AL for research (1968); to GA for weed control (1972); to NC as a potential gamefish (1972); to TX for aquaculture and bait (1979); to AZ and CA (Colorado River) for bait. It is now established in AZ-CA, in 18 FL counties, and in Tampa Bay (Courtenay et al. 1984; Page and Burr 1991, Fuller et al. 1999). It was collected in tidal creeks of Skidaway River GA in 1989 at 2-20 ppt (Hales 1991), but is not established there. In several southern states, populations of O. aureus have survived mild winters, but have been extirpated by severe winters (Fuller et al. 1999). Low winter temperatures have limited the range of O. aureus in North America (Courtenay et al. 1984; Stauffer et al. 1988), although this species appears to be the most cold-tolerant of the 'tilapias' (Zale and Gregory 1989).
Oreochromis aureus is introduced and established in South Africa, Mexico, and Puerto Rico, and has been reported from many locations in Central America, South America, and Asia (Lever 1996).
Oreochromis aureus was stocked at Brunner Island Aquaculture facility at a power plant in southern PA on Susquehanna River, 78 km above Conowingo Dam, 1982 (Skinner 1984; McKeown 1984.) The fish reproduced and survived four winters, apparently by congregating in the thermal plume of the power plant (Denoncourt et al. 1987). Because of concern by the Pennsylvania Fish Commission about the possible spread of this exotic species in Susquehanna, experiments were conducted on its tolerance to low temperature, and in Feburary 1987 power output was deliberately reduced in order to lower the temperature of the discharge canals below 5 C (Skinner 1987). No fish were collected near the power plant the following summer. Although Stauffer et al. (1988) noted the possibility of survival at other warm discharges in the river, there have been no further reports of this species in the Susquehanna or elsewhere in the Chesapeake Bay region.
Zale and Gregory (1989) found that the lethal temperature of this species was somewhat (~1 C) decreased in isosmotic (11.5 ppt, roughly equal to salinity or osmotic pressure of the fish's blood) brackish water compared to fresh or sea (35 ppt) water, and predicted that this species will range farthest north in estuaries.
History References - Courtenay et al. 1984; Denoncourt et al. 1987; Fuller et al. 1999; Hales 1991; Lever 1996; McKeown 1984; Page and Burr 1991; Skinner 1984; Skinner 1987; Stauffer et al. 1988; Zale and Gregory 1989.
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 12.0 | |||
| Salinity (‰) | 0.0 | 50.0 | 0.0 | 35.0 |
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-oligo |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | ||
| Maximum Adult Size (mm) | ||
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
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| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
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| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Oreochromis aureus (Blue Tilapia) was introduced as an experimental aquaculture fish to utilize heated effluent from the Brunton Point Steam Electric Plant (Skinner 1984). Similar experiments have been conducted in several locations in the United States (Courtenay et al. 1984), but we do not know of others in the Chesapeake watershed.
References - Courtenay et al. 1984; Skinner 1984
Economic Impacts Outside of Chesapeake Bay
Oreochromis aureus (Blue Tilapia), and several other cichlids formerly grouped in the genus Tilapia (Oreochromis spp.; Sarotherodon spp.; Tilapia spp.) are widely reared on experimental and increasingly on a commercial basis as a food fish. In the Northeast United States, 'Tilapia' farming uses greenhouses or heated effluents from industrial sources, as in the Brunner Island PA experiment (Skinner 1984). Where the climate is suitable in the Southeast and Southwest, outdoor rearing is common. Oreochromis aureus have been stocked in the southeast for a variety of reasons, including sport fishing, vegetation control, and as forage fish (Courtenay et al. 1984). This species has been collected in 13 states, and has established populations in 6 (Fuller et al. 1999). It has also been introduced to scattered locations in Mexico, South America, and southeast Asia (Lever 1996).
References - Courtenay et al. 1984; Fuller et al. 1999; Lever 1996; Skinner 1984
Ecological Impacts on Chesapeake Native Species
Oreochromis aureus (Blue Tilapia) were restricted in the Susquehanna River by their need for warm-water discharges for overwintering, although stray specimens were found at Conowingo Dam. Although no negative impacts on native fish were demonstrated, the Pennsyslvania Fish Commission decided to eradicate the fish in 1987, as a precautionary measure (Skinner 1987; Stauffer et al. 1988).
References- Skinner 1987; Stauffer et al. 1988
Ecological Impacts on Other Chesapeake Non-Native Species
Oreochromis aureus (Blue Tilapia) were restricted in the Susquehanna by their need for warm-water discharges for overwintering. Although no negative impacts on fish populations were demonstrated, the Pennsyslvania Fish Commission decided to eradicate the fish in 1987, as a precautionary measure (Skinner 1987; Stauffer et al. 1988). No impacts on other introduced biota were reported.
References- Skinner 1987; Stauffer et al. 1988
References
Courtenay, Walter R., Jr.; Hensley, Dannie A.; Taylor, Jeffrey; McCann, James A. (1984) Distribution of exotic fishes in the continental United States., In: Courtenay, Walter R., and Stauffer, Jay R.(Eds.) Distribution, Biology, and Management of Exotic Fishes. , Baltimore, MD. Pp.Denoncourt, Robert; Euston, Terry (1987) Biology of blue tilapia, Oreochromis aureus (Steindachner) in the Susquehanna River, Proceedings of the Pennsylvania Academy of Science 61: 85
Fuller, Pam. L.; Nico, Leo; Williams, J. D. (1999) Nonindigenous fishes introduced into inland waters of the United States, , Bethesda MD. Pp.
Hales, L Stanton, Jr. (1991) Occurrence of an introduced African cichlid, the Blue Tilapia, Tilapia aurea, in a tidal creek of the Skidaway River, Georgia, Brimleyana 17: 27-31
Jenkins, Robert E.; Burkhead, Noel M. (1993) Freshwater fishes of Virginia., , Bethesda, MD. Pp.
Lever, Christopher (1996) Naturalized fishes of the world., , London, England. Pp.
McKeown, Paul E. (1984) Additions to ichthyofauna of the Susquehanna River with a checklist of fishes of the Susquehanna River drainage below Conowingo Dam, Proceedings of the Pennsylvania Academy of Science 58: 187-192
Page, Lawrence M.; Burr, Brooks M. (1991) Freshwater Fishes., , Boston. Pp.
Skinner, William (1987) Eradication of Blue Tilapia (Oreochromis aureus), an exotic fish species, from the lower Susquehanna River, Proceedings of the Pennsylvania Academy of Science 61: 95-96
Skinner, William F. (1984) Oreochromis aureus (Steidachner: Cichlidae), an exotic species accidentally introduced to the lower Susquehanna River, Pennsylvania, Proceedings of the Pennsylvania Academy of Science 58: 99-100
Stauffer, Jay R., Jr.; Boltz, Suzanne E.; Boltz, Jeffrey N. (1988) Cold shock susceptibility of blue tilapia from the Susquehanna River, Pennsylvania, North American Journal of Fisheries Management 8: 329-332
Zale, Alexander V.; Gregory, Richard W. (1989) Effect of salinity on cold tolerance of juvenile blue tilapias, Transactions of the American Fisheries Society 118: 718-720