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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: Wami Tilapia

Taxonomy: available through www.itis.gov

Identification: Other commonly used names or synonyms include Tilapia hornorum, Oreochromis hornorum, and Tilapia urolepis. The Wami tilapia closely resembles O. mossambicus and was previously considered a strain (Zanzibar strain) of that species; it was later elevated to species status (i.e., Tilapia hornorum). Trewavas (1983) more recently determined T. hornorum to be a subspecies of Oreochromis urolepis (i.e., Oreochromis urolepis hornorum). Trewavas (1983) gave distinguishing characteristics, synonyms, illustrations, a key, and a discussion of hybrids. A few distinguishing characteristics were also given by Page and Burr (1991) and by Eccles (1992). A color photograph was given by Axelrod et al. (1993).

Size: 30 cm SL (Trewavas 1983).

Native Range: Tropical Africa. Wami River system, Tanzania (Trewavas 1983).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Means of Introduction: This species was first brought to California prior to the 1970s and survived in isolated colonies in relatively warm waters of the southern part of the state in the area of the Colorado Desert, Imperial and Riverside counties (Legner and Pelsue 1977; Courtenay et al. 1984), but it is unclear whether these fish were restricted to experimental ponds or whether populations were actually released into open waters. In 1972, O. urolepis was stocked into open waters by the University of California, Riverside, and by the Southeast and Orange County Mosquito Abatement districts, to control aquatic plants, mosquitoes, and chironomid midges (Legner and Pelsue 1977; Legner et al. 1980; Courtenay et al. 1984, 1986). These fish were derived from stock obtained from the University of Arizona (Legner et al. 1980).

Status: Established in southern California (Courtenay et al. 1984, 1991; Page and Burr 1991)

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: Oreochromis urolepis in the United States represent the subspecies O. urolepis hornorum (Courtenay et al. 1991). Because many hybrid O. urolepis were introduced into southern California, some doubt remains as to whether the established populations in California open waters represent pure O. urolepis strains or hybrids with O. mossambicus (Legner et al. 1980; Courtenay et al. 1984, 1991).

There are no known voucher specimens.

References: (click for full references)

Axelrod, H. R. 1993. The most complete colored lexicon of cichlids. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Courtenay, W. R., Jr., D. A. Hensley, J. N. Taylor, and J. A. McCann. 1984. Distribution of exotic fishes in the continental United States. Pages 41-77 in W. R. Courtenay, Jr., and J. R. Stauffer, Jr., editors. Distribution, biology and management of exotic fishes. Johns Hopkins University Press, Baltimore, MD.

Courtenay, W. R., Jr., D. A. Hensley, J. N. Taylor, and J. A. McCann. 1986. Distribution of exotic fishes in North America. Pages 675-698 in C. H. Hocutt, and E. O. Wiley, editors. The zoogeography of North American freshwater fishes. John Wiley and Sons, New York, NY.

Courtenay, W. R., Jr., D. P. Jennings, and J. D. Williams. 1991. Appendix 2: exotic fishes. Pages 97-107 in Robins, C. R., R. M. Bailey, C. E. Bond, J. R. Brooker, E. A. Lachner, R. N. Lea, and W. B. Scott. Common and scientific names of fishes from the United States and Canada, 5th edition. American Fisheries Society Special Publication 20. American Fisheries Society, Bethesda, MD.

Eccles, D. H. 1992. FAO species identification sheets for fishery purposes: field guide to the freshwater fishes of Tanzania. Food and Agriculture Organization of the United Nations (FAO), Rome, Italy. 145 pp.

Grana, F.  2007.  Personal communication.  Puerto Rico Department of Natural & Environmental Resources.  San Juan, PR.

Knaggs, E. H. 1977. Status of the genus Tilapia in California's estuarine and marine waters. Cal-Nevada Wildlife Transactions 1977:60-67.

Legner, E. F., and F. W. Pelsue. 1977. Adaptations of Tilapia to Culex and chironomid midge ecosystems in south California. Proceedings of the forty-fifth annual conference of the California Mosquito and Vector Control Association, Inc. 45:95-97.

Legner, E. F., R. A. Medved, F. Pelsue. 1980. Changes in chironomid breeding patterns in a paved river channel following adaptation of cichlids of the Tilapia mossambica-hornorum complex. Annual Entomological Society of America 73:293-299.

Moyle, P.B. and J. Randall. 1999. Distribution maps of fishes in California. On-line <http://ice.ucdavis.edu/aquadiv/fishcovs/wt.gif>.

Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

Trewavas, E. 1983. Tilapiine fishes of the genera Sarotherodon, Oreochromis, and Danakilia. Publication No. 898. British Museum of Natural History, London, UK.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Oreochromis urolepis

Author: Nico, L.

Peer Review Date: 7/11/2011

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.