Kolkata Municipal Corporation’s age-old drive of releasing guppy fishes in the ponds and drains to control mosquitoes could spell doom for the city’s ecosystem and force several indigenous fishes on the brink of extinction, scientists said.
Guppies are small ornamental fishes, which are a favorite among aquarium lovers. They are natives of South America, Brazil, Venezuela and Guyana and are known to feed on mosquito larvae which also make them popular for controlling diseases like malaria and dengue. But these innocent looking fishes have wrought havoc in many countries, including USA, China and Australia. They have become headache of scientists across the world because of their invasive nature.
“They can adapt to almost any kind of environment, including polluted drain water. They not only devour eggs of other fishes but are also carriers of certain fish diseases,” A Biju Kumar, who heads the aquatic biology and fisheries department of Kerala University and has been researching on invasive nature of guppies for the past several years, said.
The KMC has been releasing these fishes in the city’s drains, ponds and other perennial water bodies which are known breeding grounds of mosquitoes. Several civic bodies across India and in many other countries have also adopted similar method.
“We have been releasing guppies in the city for several years now. They are hardy fishes and can survive in drains. Almost all boroughs have developed their own small guppy-hatcheries and there is a central hatchery too. But we never had any problem,” said Debasish Biswas, the chief vector control officer of KMC.
Scientists, however, warned that this drive by the city’s civic body could backfire. Already, populations of several local varieties of fishes which were earlier found abundantly, are on the decline. The state fishery department had prepared a list of around 39 species of indigenous fish varieties which could soon go extinct few years ago.
“This is a very worrisome picture. Guppies are known worldwide as alien invasive species and could play havoc with local ecosystems. The KMC’s initiative could harm several local fish varieties. A proper study needs to be done to ascertain the damage so far,” said LK Singh, who heads the fresh water fish division at the Zoological Survey of India in Kolkata.
The state biodiversity authority has also received reports of certain other exotic fishes being spotted regularly in the city’s water bodies. This includes guppy fishes.
“The issue has been brought to our notice recently. We are planning to undertake a study to find out what change is going on in the city’s lakes and ponds,” said AK Sanyal, chairman of the West Bengal Biodiversity Board.