Invasive Species and Wetlands: Focus Ornamental Fish

By: S. Sandilyan
Agriculture Bytes

New Delhi, February 10 (G’nY News Service): The Convention on Biological Diversity (CBD 2016) has clearly stated that wetlands are essential for humans to live and prosper. Globally,wetlands are acknowledged as one of the most important bio diverse areas. Besides, more than a billion people depend on wetlands for their sustenance. Wetlands help sustain a wide variety of life on our planet, protect our coastlines, provide natural sponges against river flooding, and store carbon dioxide to regulate climate change. Thus, as the CBD has highlighted, wetlands are at the centre of livelihoods around the world, and are a major source of employment. As per the message of the executive secretary of the Convention of Biological Diversity, B F De Souza Dias, on the occasion of the World Wetlands Day on 2nd of February, 2016, “close to a billion people in Asia, Africa and the Americas depend on rice grown in the wetlands, with 80 per cent of world rice production coming from small-scale family farmers for local consumption. Another 660 million people live on fishing and aquaculture in the wetlands. International wetland tourism, besides, generates well over 1 trillion USD worldwide per year, accounting for about 9 per cent of global employment”.

Wetlands in India
India’s unique topography and climatic zones support diverse wetland habitats spread over 58.2 million hectares, as pointed out by Prasad in 2002, as also Deepa and Ramachandra in 1999; and in 2009 in their respective papers.Researchers classify Indian wetlands into two major groups: natural and man-made. Natural wetlands inIndia comprise the high altitude Himalayan lakes, wetlands in the flood plains of the major river ecosystems,saline and temporary wetlands of the arid and semi-arid regions and coastal wetlands such as lagoons, backwaters and estuaries,mangrove swamps, coral reefs and marine wetlands.

Man-made wetlands comprise inland lakes and traditional village ponds. Interestingly, man-made wetlands in our country cover 1.8 times more area as compared to natural wetlands (MoEF 1995). The 1999 study by Deepa and Ramchandra has pointed out that freshwater wetlands in India support 20 per cent of known biodiversity and harbour almost all taxonomic groups. Meanwhile, Sandilyan et. al. have pointed out in 2012 that coastal systems, such as mangroves support 4011 species of flora and fauna.

Ironically,this rich ecosystem is highly prone to invasion by alien species. Several species of alien flora and fauna pose a major danger to our wetlands. Sandilyan et. al.warned of plants like water hyacinth (Eichhorniacrassipes), giant salvinia (Salviniamolesta), andwater cabbage/lettuce(Pistiastratioies) that can cause severe damage to our wetland ecosystem.Of late, ornamental fish are posing a new risk to our wetlands as highlighted by Bijukumar, 2000,Soundararajan 2015; and Knight and Balasubramanian, 2015.

Wetland Photo 3
Suckermouth catfish (Pterygoplichthys multiradiatus) collected from Thiruvananthapuram canal, Kerela, indicate the invasion potential of the species (Photo, A. Bijukumar)

Studies in India have been recording the presence of several exotic ornamental fish ranging from the tiny guppy (Poeciliareticulata) to the aggressive red piranha (Pygocentrusnattereri) in rivers, lakes, traditional village ponds and other inland freshwater bodies. A number of exotic ornamental species have already reproduced in our inland wetlands. Their numbers continue to rise as more than 200 alien aquarium fish species are bred in different parts of India by untrained local vendors as pointed out is a study by Ghosh 2003; and Tripathi, 2015.

Breeding sites are in the form of small cement cisterns or earthen ponds, plastic-lined pools, homestead ponds and granite quarries. Since most such sites are not properly protected/fenced, these exotic fish can effortlessly enter into adjoining natural ecosystems during monsoon floodwaters and end up as a threat to native diversity (Krishnakumar et. al. 2009;Singh and Lakra, 2011;Soundararajan et. al.2015).

Studies undertaken globally emphasise how alien fish frequently alter aquatic ecology by changing the water quality and cause the extinction of native fish through predation (destroying the eggs, larvae, sub adult and adult), damaging the aquatic vegetation, exploiting food resources and polluting the natural gene pools. (Pimentel 2002; Liang et. al. 2006).

So far, there is no such detailed study conducted in India on the impact of ornamental fish on every tropic level. Whatever little work has been done on the matter, pertains to the presence of such fish in inland waters, and stops short on examining their impact on the natural ecosystem.

The decline of native fish varieties can affect the livelihood, health and general well-being of rural and indigenous communities drastically. Hence, it is necessary to monitor the movement and introduction of ornamental fish in the wild, particularly where India’s natural and manmade wetlands are concerned, and protect our natural biodiversity.


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CBDa.(2016). Wetlands and sustainable livelihood [PressRelease]. Retreived from

CBDb. (2016). Message of the executive secretary of the convention on biological diversity Braulio F.De Souza Dias. Retrieved Feburary 2, 2016, from

Deepa, R.S. & T.V. Ramachandra.(1999,January).Impact of Urbanization in the interconnectivity of wetlands.Paper presented at the National Symposium on Remote Sensing Applications for Natural Resources: Retrospective and perspective.

Ghosh A, Mahapatra, BK, Dutta, NC.(2003).Ornamental fish farming–successful small-scale aqua business in India. Aquaculture Asia 8(3). 14–16.

Kathiresan, RM. (2012). Sustainable options for the integrated management of invasive alien weed water hyacinth (Eichhornia crassipes) in aquatic system. Paper presented at Proceedings of 6th Intel Weed Science Congress (IWSC),Hangzhou, China.

Knight, J.D.M. and Balasubramanian, S. (2015). On a record of two alien fish species (Teleostei: Osphronemidae) from the natural waters of Chennai, Tamil Nadu, India. Journal of Threatened Taxa 7(3), 7044–7046.doi:

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Prasad, S.N., Ramachandra, T.V., Ahalya, N., Sengupta, T., Tiwari, V.S.,Vijayan,V.S. and Lalitha Vijayan.(2002). Conservation of wetlands of India _ a review. Tropical Ecology, 43(1),173 – 186.

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Singh, A.K. and Lakra, W.S. (2011). Risk and benefit assessment of alien fish species of the aquaculture and aquarium trade into India. Reviews in Aquaculture,3, 3–18.

Soundararajan, N., Mohan, R.R., Kamaladhasan, N et al.(2015). On-line trade of aesthetic exotic organisms: sword of Damocles?. Current Science,109 (8),1404-1410.

Tripathi, A.(2015). Monogenoidea on exotic Indian freshwater fish. 3. Are Indian guidelines for importation of exotic aquarium fish useful and can they be implemented; The case of Neotropical Gussevia spiralocirra Kohn and Paperna, 1964. Current Science, 108(11),2101-2105.

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