Exotic weeds like species of Salvinia molesta, Eichhornia, etc. which reached the coastal belt of Kerala have become gregarious in the inland waters, ponds, canals, etc. in the lowland area. Being very aggressive in nature, they suppress the natural flora and fauna and pollute water bodies and prevent free flow of water. Such weeds came to the coast of Kerala by way of natural distribution through water or by land as in the case of Azalla, Salvinia and Eichhornia. The exotic fish Tilapia (Oreachromis massambica) and the African Catfish (Clarias gareipinus) which got introduced into the water bodies of Kerala have become a threat to indigenous fish fauna, on which they feed.