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The Louisiana crayfish Procambarus clarkii, also known as the red swamp crayfish, supports a lucrative aquaculture industry in its native range, and is a popular component of the region’s Cajun cuisine. Over the last 50 years it has been introduced to Africa, Europe and Asia, in most cases with negative consequences.
Another invasive alien species that may have contributed to the periodic collapse of Lake Naivasha’s aquatic plants is the coypu or nutria, Myocastor coypus. This large semi-aquatic rodent is indigenous to South America, but was introduced to East Africa, North America, Europe and Asia to be raised for its fur. Since escaping from fur farms it has established large feral populations in some areas, causing considerable damage in wetlands, rivers, dams and irrigation canals by bur rowing into banks and dykes.
Mass murder in Lake Victoria: It’s been called the biggest mass extinction of vertebrates in recorded history – at least 200 fish species erased from existence by a ravenous predator, the Nile perch
The common carp Cyprinus carpio is undoubtedly the most widespread inavasive alien fish in Africa, found in most of the continent's countries. Native to to parts of Europe and Asia, it was one of the first species to be introduced outside its natural range, and now has a global distribution. The carp was deliberately introduced for food in most cases, as it provides a cheap source of protein. In some regions of the world it was introduced for sport-fishing, but although it is considered a premier sport-fish in Europe and Asia, it is among the least favoured targets of anglers elsewhere, and is generally regarded as a pest because of the damage it causes to freshwater habitats. Furthermore, its introduction has resulted in the spread of a number of fish parasites.
Tilapia are freshwater fishes belonging to the cichlid family. The various species are indigenous to different parts of Africa and the Middle East, but a number of them have been introduced to other African areas and the rest of the world. In some instances they were introduced as sport-fish, aquarium fish, or even as biocontrol agents to control waterweed or filamentous algae, but in most cases they were intended for aquaculture. However, some species have escaped or been deliberately released from captivity, and have established invasive populations in the wild.
As its name suggests, the native range of the Indian house crow, Corvus splendens, is centered in India, and extends from Iran in the west to Burma in the east. However, the bird was introduced to Africa in the 1890s, reportedly via Zanzibar, where it was brought to help keep the island free of rubbish. It subsequently spread along the coast of East Africa by hitching lifts on ships, and is now found right down to Cape Town at the southern tip of Africa. The crow also inhabits parts of the North African coast bordering the Suez Canal and Mediterranean Sea. It mainly occurs in urban and suburban environments, living in close association with humans.
The house sparrow Passer domesticus is indigenous to Eurasia and North Africa. It is believed to have been introduced to southern Africa from India in the late 1890s, probably as a pet of Indian labourers working in the sugarcane fields around Durban, South Africa. Within 50 years it was widespread in KwaZulu-Natal province, and in 1948 was reported to have crossed the Drakensberg mountain range into the interior of South Africa. Thereafter, colonisation of the rest of southern and central Africa was very rapid, supplemented by additional minor introductions of escaped aviary birds in East London in South Africa, Harare in Zimbabwe, Maputo in Mozambique, and probably elsewhere. The house sparrow has also been introduced to east Africa, where it is found on the coast of Kenya and along the railway route to Nairobi.
Some invasive alien species have a negative impact on biodiversity not by displacing indigenous species through predation or competition,but by compromising their genetic integrity.
The European, or common starling, Sturnus vulgarisis native to Eurasia, migrating into North Africa to over-winter in more temperate African countries. The bird was intentionally introduced to South Africa, New Zealand, Australia and North America, mainly for aesthetic reasons but sometimes also to control insect pests. Ironically, it is now considered a pest itself, largely because the noisy habits and messy droppings of huge flocks are esthetically unappealing.
The rosy wolf snail Euglandina rosea is a predatory terrestrial snail that is native to Latin America and the south-eastern United States. It has become invasive in a number of island states off the African coast, including Mauritius, Reunion, Madagascar and the Seychelles.
The Argentine ant Linepithema humile has spread from its native range in South America to parts of all other continents except Antarctica. Where it has become established, it is:• a domestic nuisance in urban areas• a destructive pest in agricultural areas, and• an aggressive invader in natural areas, negatively impacting biodiversity both by killing and displacing other species and by altering ecosystem processes such as pollination and seed dispersal.