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   Oreochromis aureus (fish)   
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    Taxonomic name: Oreochromis aureus (Steindachner, 1864)
    Synonyms: Chromis aureus (Steindachner, 1864), Sarotherodon aureus (Steindachner, 1864), Tilapia aurea exul (Steindachner, 1864), Tilapia aurea (Steindachner, 1864), Tilapia kacherbi (Wunder, 1960), Tilapia kashabi (Elster, 1958), Tilapia lemassoni (Blache & Milton, 1960), Tilapia monodi (Daget, 1954)
    Common names: abiad hasani (Arabic-Egypt), amnon hayaor (Hebrew-Israel), amnun hayarden (Hebrew-Israel), amnun yarden (Hebrew-Israel), an-boh boh (Sierra Leone), biering-pill (Chad), blue tilapia (English-USA, UK, Mexico, Fiji, Taiwan), bolti azrak (Arabic-Egypt), epia (Nigeria), fartere (Cameroon), gargassa (Cameroon), gargaza (Nigeria), Goldtilapia (German-Germany), guldtilapia (Swedish-Sweden), holinga (Cameroon), Ifunu (Nigeria), Israeli tilapia (English-South Africa), Israelse tilapia (Afrikaans-South Africa), Jordan St. peter's fish (English-Israel), karpassa (Cameroon), karwa (Nigeria), kpeloi (Sierra Leone), kultatilapia (Finnish-Finland), kurpertilapia (English-Eqypt), mpupa (Nigeria), musht lubbad (Arabic-Israel), partere (Cameroon), sale (Chad), sayray (Sierra Leone), sohn-pill (Chad), tilapia (English-Nigeria, Philippines), tilapia azul (Spanish-Mexico), tome (Nigeria), tsokungi (Nigeria), ukuobu (Nigeria), waas (Senegal), wass khoss (Senegal), wass xos (Senegal), wass-bor (Senegal)
    Organism type: fish
    Oreochromis aureus (blue tilapia) is native to parts of Africa and the Middle East and is an important food source throughout the world. Oreochromis aureus are easily raised as they are resilient and prolific and have a high grain-to-feed conversion rate. Worldwide introductions for use in aquaculture have provided an essential source of protein to many nations. However, these characteristics have allowed them to dominate many of their introduced ranges by displacing native species and restructuring aquatic communities in areas where they have established by means of escape from confinement or deliberate release.
    Oreochromis aureus is a cichlid blue and silver in color with 18-26 gill rakers, 16 dorsal spines, and 3 anal spines.The caudial fin has a broad pink to red distal margin. Males are significantly larger then females with a max length of 50.8 cm. Breeding males exhibit an intense bright metallic blue on their head, a vermillion edge to their dorsal fin, and a more intense pink on the caudal fin. Breeding females exhibit paler more orange edges to their dorsal and caudal fins (GSMFC, 2003; FishBase, 2007)
    Similar Species
    Oreochromis niloticus

    Occurs in:
    estuarine habitats, lakes, water courses
    Habitat description
    Oreochromis aureus is benthopelagic and potamodromous. It prefers tropical climate but is fairly cold tolerant. It occurs in temperatures 8°-30° C and freshwater to fairly brackish salinities. O. aurues is considered hardy and tolerant to a wide range of water quality and habitat conditions (McKaye et al. 1995; FishBase, 2007).
    General impacts
    Oreochromis aureus competes with native fishes for food, spawning area, and space, and exhibits aggressive behavior. They have become the dominant species in many of their introduced ranges. Several introductions have correlated with and are believed to cause reductions in abundance of native fishes and even molluscs. Blue tilapia structure phytoplankton communities by their feeding preference of specific algae, having significant effects on the entire community ecology. Some reports maintain certain introduced areas have lost most and nearly all native fishes (McDonald, 1987; GSMFC, 2003; FishBase, 2007; Nico, 2007).
    Oreochromis aureus is a prolific and tolerant species introduced worldwide for aquaculture, angling, and the control of aquatic vegetation. They are popularly used for hybridization in producing all male populations (FishBase, 2007). Power companies have introduced O. aureus for food and sport, as well as vegetation control, in heated effluent ponds used to cool effluents from plants which are too warm to support native fish (Nico, 2007).
    Oreochromis aureus is believed to have been documented as Oreochromis nilotica in many accounts since many identifications were made before the two species were differentiated. O. aureus may be identified by its lack of dark vertical stripes present on the caudal fins of O. niloticus (GSMFC, 2003; Nico, 2007).
    Geographical range
    Native range: Cameroon, Chad, Egypt, Israel, Jordan, Mali, Niger, Nigeria, Saudi Arabia, Senegal.
    Known introduced range: Antigua and Barbados, Bahamas, Brazil, China, Coasta Rica, Cote d'Ivoire, Cuba, Cyprus, Dominica, Dominican Republic, El Slavidor, French Polynesia, Guatemala, Gulf of Mexico, Haiti, Japan, Kuwait, Mexico, Myanmar, Neth Antilles, Nicaragua, Pakistan, Panama, Peru, Philippines, Puerto Rico, Russian Federation, Singapore, South Africa, Syrian Arab Republic, Taiwan, Thailand, Turkey, Uganda, United Arab Emirates, United States, Zambia (McDonald, 1987; GSMFC, 2003; FishBase, 2007; Nico, 2007).
    Introduction pathways to new locations
    Aquaculture: Oreochromis aureus are an extremely popular species in aquaculture since they are highly prolific and tolerant to a range of environments. Referred to as "aquatic chicken" because they are an affordable high-yield source of protien, tilapia have been introduced throughout the world (Canonico et al. 2005).
    Biological control: Many introductions of Oreochromis aureus have been to control aquatic vegetation (Nico, 2007).
    Stocking: Oreochromis aureus, a tolerant and prolific species has been stocked as a food species in rivers, lakes, and ponds throughout the world (Nico, 2007).

    Local dispersal methods
    Aquaculture (local):
    Escape from confinement: Most alien established populations of Oreochromis aureus have resulted from their escape from confinement in aquaculture or experitmental locations (Nico, 2007).
    Intentional release:
    Natural dispersal (local):
    Management information
    Preventative measures: The use of potentially invasive alien species for aquaculture and their accidental release/or escape can have negative impacts on native biodiversity and ecosystems. Hewitt et al, (2006) Alien Species in Aquaculture: Considerations for responsible use aims to first provide decision makers and managers with information on the existing international and regional regulations that address the use of alien species in aquaculture, either directly or indirectly; and three examples of national responses to this issue (Australia, New Zealand and Chile). The publication also provides recommendations for a ‘simple’ set of guidelines and principles for developing countries that can be applied at a regional or domestic level for the responsible management of Alien Species use in aquaculture development. These guidelines focus primarily on marine systems, however may equally be applied to freshwater.

    Copp et al, (2005) Risk identification and assessment of non-native freshwater fishes presents a conceptual risk assessment approach for freshwater fish species that addresses the first two elements (hazard identification, hazard assessment) of the UK environmental risk strategy. The paper presents a few worked examples of assessments on species to facilitate discussion. The electronic Decision-support tools- Invasive-species identification tool kits that includes a freshwater and marine fish invasives scoring kit are made available on the Cefas (Centre for Environment, Fisheries & Aquaculture Science) page for free download (subject to Crown Copyright (2007-2008)).

    Most management techniques to control undesired fish populations are not effective for control of tilapia. Prevention of escape and care in stocking of Oreochromis aureus can effectively prevent their establishment of wild populations. Totally closed systems should always be used when cultivating blue tilapia, and only in watersheds where tilapia have already penetrated. O. aureus aquaculture should be banned from watersheds and lakes in which they have not become established (McCrary et al. 2007).

    Physical: Oreochromis aureus populations of Brunner Island, Pennsylvania were eradicated in 1986, when condenser cooling water was deliberately and temporarily released at lethal, low temperature. One study recommended the temperature be brought to 5°C for 16 hours to effectively eradicate O. aureus (Stauffer et al. 1988; Costa-Pierce, 2001; Nico, 2007).

    Biological: The use of predatory fish Morone saxatilis X Morone chrysops and Sciaenops ocellatus has been effectively employed to reduce wild spawning among tilapia hybrids (Oreochromis niloticus X Oreochromis aureus) in aquaculture growout ponds. However, such introductions in the wild would have their own ecological effects. Other known predators and possible controls include: snakehead (Channa striata), tarpon (Megalops cyprinoides), Nile perch (Lates niloticus), Hemichromis fasciatus, and Cichlasoma managuens (Milstein et al. 2000).
    A management program in Lake Nicaragua to increase the abundance of potential predators of large tilapias, including Oreochromis aureus such as alligators, Crocodrilus acutus, Crocodrilus gars and Crocodrilus elasmobranchs, all vastly reduced from just a few decades earlier, has been recommended (McCrary et al. 2007).

    Integrated management: Promotion and augmentation of fishing pressure on O. aureus in order to reduce the average fish size and thereby free niche space for other fishes is another recommended means of controlling their populations (McCrary et al. 2007).

    Oreochromis aureus feeds primarily on phytoplankton and epiphytic algae, but has a wide diet including insects, zooplankton, vascular plants, and larval and juvenile fishes. Young have a more varied diet which includes large quanities of copepods and cladocerans (McKaye et al. 1995; GSMFC, 2003).
    Ovophilic: external fertilization, capable of breeding in freshwater and brackish water. Reproduction of Oreochromis aureus is stimulated by long photoperiods and requires a minimum temperature of 20° C. Males dig a spawning pit, usually among weedy areas, which they defend aggressively. They visit schools of females to attract a mate. Courting behaviour includes lateral display, nipping, and tail flapping by both sexes. Females deposit eggs in single clutches. A maternal mouthbrooder, females take the eggs into their mouth as soon as they are fertilized and swim to deeper waters while the male attempts to spawn with another female. Hatching occurs about 3 days after oviposition, and juveniles remain in their mother mouth until they are about 1cm long. They school near their mothers mouth for about five days before going on their own. O. Aureus does not have strict habitat requirements for reproduction, so introduced populations can take up all available habitat for breeding sites (McKaye et al. 1995; FishBase, 2007)
    Lifecycle stages
    Hatching occurs about 3 days after oviposition, and juveniles remain in their mother mouth until they are about 1cm long. They school near their mothers mouth for about five days before going on their own. Young are particulate feeders during larval and juvenile stages (McKaye et al. 1995; FishBase, 2007).
    Reviewed by: Pam Fuller USGS/BRD, Nonindigenous Aquatic Species Program. Florida Integrated Science Center. USA
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Thursday, 27 March 2008

ISSG Landcare Research NBII IUCN University of Auckland