Proliferation of invasive water weeds and exotic species of fish has played havoc with the ecosystem of the Veli and Aakkulam Lakes and the feeder canals, threatening the livelihood of inland fishermen and affecting backwater tourism.Water hyacinth is the most threatening invasive species in Kerala.Water hyacinth, a fast-growing plant with populations known to double in as little as 12 days, blocks waterways, limiting boat traffic, swimming and fishing. The weed prevents sunlight and oxygen from reaching the water column and submerged plants. By crowding out native aquatic plants, it dramatically reduces biological diversity in aquatic ecosystems. Listed as one the 100 most dangerous invasive alien species of the world, this aquatic weed native to South America, was introduced to the country as an ornamental plant for cultivation in ponds because of its beautiful, large purple and violet flowers. Today, it invades more than 50 countries in five continents.