CHENNAI: Greater Chennai Corporation is introducing mosquito fish, scientifically known as Gambusia affinis, in open wells and clean water bodies across its 15 zones to contain mosquito breeding According to sources in the civic body, 4.5 lakh fish will be introduced in a phased manner in wells and water bodies across the zones for now. The civic body has identified more than four lakh wells.In Thiru Vi Ka Nagar, Valsaravakkam and Kodambakkam, the fish have already been introduced to kill the larva of dengue-causing mosquitoes which breed in fresh water.“This is a biological control measure against dengue-causing Aedes aegypti. At least three pairs of fish are needed per well. Currently, these are being introduced in areas with a high water table level and for the rest of the areas, the fish will be introduced as rain starts,” said an official, adding that the surface-feeders will survive only if the depth of water in the well is not more than 25ft. The official said the civic body, which is currently procuring the species from the fisheries department, plans to create natural hatcheries by introducing the fish in wells. “Each fish can consume up to 300 larvae per day. As these are capable of breeding fast and the freshwater bodies will sustain these until summer, natural hatcheries can be formed,” the official said.In Thiru Vi Ka zone, 3,800 wells were identified, and 12,000 fish were introduced in the open wells of wards 64, 65 and 67. “The fish was introduced in areas where the water table was decent. Kolathur area was found to have several open wells,” said an official.A senior official said each zone has been asked to put forth its demand for the fish. “The plan is to introduce at least 50 to 100 fish per well and it will be done in a phased manner. Some zones have sought at least 50,000 fish,” the official said.Globally, methods used to tackle mosquito larva breeding are divided into chemical, biological, integrated and genetic controls. Corporation deploys chemical methods such as larvicide and fogging, besides now using fish as a biological measure. Mosquitofish and guppy fish are the two types of exotic fish used for mosquito control.

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