CHENNAI: The beautiful goldfish in your fish tank is also one of the most perseverant pests that could ruin the local aquatic ecosystem. And many of them are already in the lakes, ponds and rivers, fear experts.
During the devastating Chennai floods late last year, many ornamental fish varieties could have escaped from the backyards of houses near Retteri Lake in Kolathur, a hub of ornamental fish trade in the country. “A good number of locals are into the business, most of them running breeding units in small cement tanks or earthen ponds. At least 600 species are available in the area. There is a risk of them entering the waterbodies due to the lack of protection or fencing,” S Sandiliyan of the Centre for Biodiversity Policy and Law, National Biodiversity Authority, told Express.
In an attempt to raise awareness among the people and policymakers, Sandilyan published an article in the journal Current Science titled Occurrence of Ornamental Fishes: A looming danger for Inland Fish Diversity of India, highlighting how there was an increasing number of reports from around the country about exotic fish varieties found in local habitats.
Alien species were found in River Chalakudy in the Western Ghats in neighbouring Kerala, a biodiversity hotspot that harbours 16 endangered and four critically endangered species and where researchers have found 27 ornamental species, in Ameenpur lake in Telangana that was declared as a biodiversity heritage site by the State government and also the Vaigai. In most cases, the hobbyists who kept ornamental fish varieties were found to be the culprits. They released it into the wild when they got bored or when it became too big for the aquaria, Sandilyan said in his paper. Once out of the enclosure, these fish types feed faster than the local ones and many a time, feed on the eggs and larvae of the local species. They are often live carriers of pathogens and parasites, leading to outbreak of exotic diseases.
The threat is restricted not only to India, but across the globe. An estimated 20 per cent of freshwater fish fauna are already extinct or are on the verge of extinction due to this.
According to David L Morgan of Freshwater Fish Group and Fish Health Unit, Murdoch University in western Australia, invasive species create all sorts of problems to the native ones and their environments, including introduction of diseases and parasites, competition for habitat, predation and aggression. Making people aware of the risk of introducing non-native species was paramount, he said in an email. “The government should constitute an authority to monitor the entry of invasive species,” said former director of Zoological Survey of India K Venkatraman. Recalling his days in Kolkata, he said such ‘alien’ invasions had led to the disappearance of 17 native species in West Bengal. “The issue is alien species do not have a predator in Indian waters, unlike in their place of origin,” he said.
According to scientists in the National Bureau of Fish Genetic Resources, conservation of fish varieties has never been adequately addressed in the country, mainly due to the lack of scientific data. The Ministry of Environment and Forest had devised an action plan. Currently, the country has identified 31 aquaculture species, 600 ornamental varieties and two species of larvicidal fish types as exotic. But Sandiliyan said that was not enough.
The harmful role of alien fish species in aquatic diversity and commercial aquaculture has not been properly addressed in several parts of country, he added.