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Main articles: Tilapia

A number of tilapiine cichlids that are native to Africa and the Levant have been widely introduced into tropical fresh and brackish waters around the world. In some cases, the introductions were deliberate, for example to control invasive aquatic plants, as in the U.S. states of Florida and Texas. ^[1] Across much of Asia and Africa they have been introduced into ponds and waterways for the purposes of aquaculture. ^[2] In other cases, unwanted fish have been released by aquarists or ornamental fish farmers into the wild.^{[3] [4]}
Because tilapiine cichlids are generally large, fast growing, breed rapidly, and tolerate a wide variety of water conditions (even marine conditions), once introduced into a habitat they generally establish themselves very quickly. In doing so they compete with native fish fauna, create turbidity in the water (by digging) thus reducing the light available for aquatic plants, and eating certain types of aquatic plants causing changes in local aquatic flora. Such problems have been observed in many different places, including Australia, Philippines, and the United States.^{[5] [6] [7]}

Contents

Singapore

Solomon Islands

United States

Australia

Galapagos Islands, Ecuador

See also

References

Singapore

In Singapore, ''Oreochromis mossambicus'' was introduced from Java by the Japanese during World War II, hence its local names, 'Japanese fish' and 'Java fish'. It was formerly very abundant in fresh and brackish waters and in the sea off the north coast. However, since the late 1980s, feral tilapiine cichlid populations in most locations have crashed, possibly due to cross breeding with more recently introduced tilapiine cichlid hybrids (red tilapia ''O. mossambicus'' x ''O. niloticus'', possibly also ''O. honorum'' and ''O. aureus''). The offspring of the crosses may be strongly sex skewed in favour of males, and inter-species crosses tend to produce fewer fry per brood than single species spawns, thus causing the population to decline, and hybrids with ''O. niloticus'' may inherit the lower salinity tolerance of that species, thus restricting the habitats where these tilapiine cichlids are found.

Solomon Islands

On Rennell Island (Solomon Islands), the Rennell Island Teal became extinct after introduced ''Oreochromis mossambicus'' preyed on the young birds.

United States

Salton Sea in Southern California is home to a large population of ''Oreochromis mossambicus'' known locally as 'Salton Sea tilapia'. How they got into the Salton Sea is not known for certain.^[8] The Salton Sea tilapia feed on plant material, phytoplankton (particularly diatoms), copepods, rotifers, barnacle larvae, and small annelid worms.^[9] One peculiarity of the Salton Sea are the periodic algal blooms that cause the fish, including the Salton Sea tilapia, to die in massive numbers, causing a particularly nasty smell.^[10]

Australia

Shortly after their first importations to Australia in the 1970s aquarium trade, tilapia were introduced into the warm waters of North Queensland dams for weed and mosquito control. ^[11] Later genetic studies indicated that at least two separate introductions to the native creeks and rivers occurred.^[12] As early as 1979, there were established populations of ''Tilapia mariae'' and ''Cichlasoma nigrofasciatum'' in the cooler climate of Victoria, in a pond warmed by a power station ^[13]. In 1981 they were also noted to be present in the waters of Carnarvon, Western Australia ^[14].
Ten years later it was noted that there were established feral populations of tilapia throughout the waters of Queensland and Western Australia, and their geographical range was continuing to increase ^[15]. By 1991 the waters surrounding the Queensland cities of Brisbane, Townsville, and the Gascoyne River in Western Australia were filled with ''Oreochromis mossambicus''. It was also found that ''Tilapia mariae'' was a much less commonly found exotic, though its trapping in rivers north of Cairns indicated that at the time it was possibly extending its range into its preferred water temperature ranges, and that it had a great capacity for tolerating a wide range of salinity levels.
Impacts on Australian rivers, creeks and ponds have been great, particularly the dramatic decreases in native fish populations due to predation and competition for food by the fast breeding tilapia that consume a vast range of food sources ^[16]. Further habitat impacts include increases in local turbidity levels from nesting behaviours. Native fish, invertebrates, and other organisms also experience reduced access to cover through the aggressive territorial defence of breeding and feeding sites by some tilapia species.

Galapagos Islands, Ecuador

Tilapia have been introduced to Laguna Junco, an older volcanic caldera.^[17] There are no native freshwater fishes in the Galapagos, but there are several native invertebrates that spend all or part of their lifecycle in freshwater. At least one, the Galapagos dragonfly, is endemic. Tilapia must be presumed to pose a threat to these invertebrates. The Ecuadorian Park Service is currently (2007) planning an eradication attempt, with the assistance of US Aid for International Development and the US Geological Survey.
Tilapia have been introduced to the mainland of Ecuador, as well as to much of the rest of Latin America, as a fish culture organism.

See also

★ Invasive species

★ Tilapiine cichlid

★ Tilapia

★ Tilapia in aquaculture

★ Genus ''Tilapia''

★ Genus ''Sarotherodon''

★ Genus ''Oreochromis''

References

1. Florida's Exotic Freshwater Fishes
2. Introduction of tilapia species and constraints to tilapia farming in Fiji
3. Fact Sheet for Tilapia zilli (Gervais, 1848)
4. Nonindigenous Fishes of Florida - With a Focus on South Florida
5. Tilapias as Alien Aquatics in Asia and the Pacific:
A Review, FAO Fisheries Technical Paper 453 Sena De Silva ''et al''
6. Tilapia mariae
7. Tilapia - NSW DPI - Fisheries
8. Salton Sea 101
9. Riedel, Ralf; Costa-Pierce, Barry A. (2005-04) "Feeding Ecology of Salton Sea Tilapia (Oreochromis spp.)", ''Bulletin, Southern California Academy of Sciences'', Vol 104, Isssue 1. pp 26-36
10. Salton Sea 101
11. Tilapia spreads in nth Qld
12. An assessment of genetic differentiation among feral Australian tilapia populations
13. Occurence of exotic tropical fish in the cooling pondage of a power station in temperate south-eastern Australia
14. Aquatic Invaders - Introduced species are a threat to our aquatic biodiversity: Tilapia or Mozambique Mouthbrooder
15. An assessment of genetic differentiation among feral Australian tilapia populations
16. Press Release - Tilapia under attack
17. Galapagos Conservation Trust