CHENNAI: A recently-published study has revealed the presence of two invasive species of fishes in Chembarambakkam and Red Hills reservoirs, raising concern among experts. Both are ornamental fishes that enter new places through aquarium trade.
A study by J D Marcus Knight and Shankar Balasubramanian, published in the latest issue of Journal of Threatened Taxa, has revealed the existence of two invasive species, Trichopsis vittata and Macropodus opercularis, belonging to the Osphronemidae family, in Chembarambakkam and Red Hills lakes respectively.
The survey for the study was conducted last year between April and June in water bodies around Chennai.
The study done by Knight states that Trichopsis vittata is native to South East Asia and has established a viable population in Florida. Their extermination, it adds, is impossible. Similarly, Macropodus opercularis is also a native to South East Asia and China and has established non-native populations in Florida, Singapore and Japan, which are also the hub of ornamental fish trade, similar to Chennai.
Incidentally, according to the journal, over 150 species of vertebrates, invertebrates, plants and microbes (including pathogens) that have invaded India’s natural ecosystems come from aquariums and ornamental aquatic culture.
Also, one-third of aquatic species on the International Union for Conservation of Nature (IUCN) Invasive Species Specialist Group’s list of 100 worst invasive species are from aquarium or ornamental releases.
Knight also states that it is not only the aquariums but also the river linking projects that are bringing non-native species into Chennai.
Such alien species, say experts, threaten the local species by disturbing the food chain. This situation has risen because the government lacks norms to regulate the aquarium trade, according to K Venkataraman, director, Zoological Survey of India.
Reacting to a query about alien fish species found in the natural waters of Chennai, Venkataraman says that there is need for the Union government to set up a separate authority to regulate invasive species.
Venkataraman stresses the need for creating awareness among the quarantine department, customs and forest department on the threat to native species by alien species.
The problem of alien species is not limited to water bodies here. A newsletter of IUCN this year brought to light the presence of red-bellied piranha in Godavari river. The fish was illegally introduced for aquarium keeping and is now found occasionally along with other catch at Dhawaleshwarm barrage in Rajamundhry.
However, the government is not maintaining any record of invasive alien species. Knight, in his study, states that unless stringent measures are taken to monitor the aquarium fish trade and the accidental release of exotic species into water bodies including man-made lakes as well as tanks, they would emerge as breeding grounds for invasive fish that will eventually wipe out native freshwater fishes.
Even the IUCN guideline stresses the need to focus on preventing the loss of native biodiversity caused by invasive alien species.
Alien Species lurking in City waters Trichopsis vittata
Origin: South East Asia; Found in: Chembarambakkam lake; Discovered: 2014
Macropodus opercularis Origin: South east Asia;
Found in: Red Hills; Discovered: 2014
Giant gourami
Origin: South east Asia; Introduced: 1866;
Recordings: Adyar River
Tropical American Catfish
(Pterygoplichthys multiradiatus)
Origin: Possibly US; Discovered in: Adyar Basin;
Threat: Disrupts aquatic food chain; Discovered: Around 2006-2009