Freshwater aquaculture (2+1)

Unit 5 - Impact of exotic (Introduced) species

5.1. Impact of exotic species

• Introductions are movements beyond the present geographical range of a species and are intended to insert totally new taxa into flora and fauna.
• Species are introduced beyond their geographical range for the purpose of aquaculture; ornamental fish trade, enhance genetic characteristics or re-establish a species that has totally failed.
• About 168 species from 37 families have been reported to be introduced world over. Out of these, 67 species have established themselves in the new environment and 7 species have become pests.
• A few of the important species that were introduced into India are the Chinese carps namely silver carp, grass carp and common carp. They are used in composite fish culture along with the Indian major carps catla, rohu and mrigal. The Chinese carps were also introduced into the reservoirs to enhance fish production.
• Tilapia was also introduced into natural water bodies, where it has completely established itself.
• The illegal introduction into India was the African catfish.
• Clarias gariepinnus which is a highly predatory has a serious potential to destroy native species. It has already established in many parts of India and is presumably causing extensive harm to the native species.
• The Thai catfish Pangsiodan hypothalamus has recently been introduced to India to augment fish production.
• Apart from these the mosquito fish Gambusia affinis was introduced to control mosquito larvae – the adult mosquitoes spread the malaria parasite Plasmodium
• Many ornamental fish have been introduced all over the world away from their natural habitat.