Alien fish species have received comparatively attention internationally being a species that challenges worldwide by aquatic invasion. With relatively more adequate information on the invasive fish species, it will allow a more complete set of analysis and comparison. The biological exchange of invasive species has caused a relatively crucial threat to the biodiversity of freshwater ecosystems compared to all the others. This is mainly due to the intentional as well as the unintentional release of organisms to the freshwater ecosystem (1).
Definition of Invasive species
Invasive species are animals, plants, parasites or diseases causing organisms that are established outside of their native range and becomes pests. It is also possible for native species in becoming invasive species as they are introduced into a foreign environment. These damaging species are introduced into the new environment either as pets, as lifestock, as pack animals, for sports, to control other pests, to prevent erosion. The animals that were mainly introduced to control other pests often became the pests themselves, such as the mosquitofish and cane toads, while the plants that were introduced to prevent erosion, frequently spread successfully and established their species. Invasive species also include disease causing organisms, such as fungi and viruses(2).
Impacts caused by introduced/exotic fish species
The impacts that are caused by exotic fishes can be predating on native species, competing with native fishes for food and habitat, exterminating aquatic vegetation, disturbing sediments of the lake and introducing disease or parasites.
There are abundant examples of the consequences caused by introducing the exotic species, such as introduction of bighead and silver carp in China, Asian carp in the Mississippi river of the United States, several different kinds of carps in Mauritius of Africa and European carps in Brazil, South America(2).
How do people control or prevent these impacts from the introduction of exotic fish species?
There are generally two types of methods of control, which are Conventional Control and Biological Control. Conventional control is mainly focused on techniques that control invasive species. For example, by trapping, poisoning and shooting. As for biological controlling, they are generally methods that control pest by their natural predators, parasites and disease-carrying bacteria or viruses. Since it is possible for the biological control agents to become pests in the applied area as well, much noticed should be placed on side effects of the biological control(2).
