Some alien (exotic) species become invasive and cause maximum harmful imapct and the extinction of the indigenous species.
Nile perch, a large predator fish was introduced in lake Victoria (East Africa) caused the extinction of an ecologically unique species of cichlid fish in the lake.
Invasive weed species like parthenium, Lantana and Eicchornia caused environmental damage and pose threat to our native species.
Introduction of African catfish (Clarias gariepinus) for aqua-culture purpose is posin g a threat to the indigenous cat fishes of Indian rivers.
