"Alien species are highly invasive and are a threat to local species". Substantiate this with any two examples.

Explanation

a) The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
b) The environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (parthenium), Lantana and wsater hyacinth (Eicchornia).
c) Illegal introduction of the African catfish Clarias gariepinus for aqua culture purpose is posing a threat to the indigenous catfishes in our rivers.