Guppy released into river a threat to native fish: Expert

Neha Basudkar
Friday, 15 March 2019

Ghate, former Head of Department (HoD), Zoology, Modern College said, “Guppy, gambush and tilapia are destroying the ecosystem of the rivers.” 

PUNE: Since the rising temperature is linked with increase in number of mosquitoes, the Pune Municipal Corporation (PMC) has started over 188 production units of guppy fishes that eat mosquito larvae to curb the mosquito population. However, according to zoology expert Hemant Ghate, the guppy is a threat to the native fishes of the river waters. 

Ghate, former Head of Department (HoD), Zoology, Modern College said, “Guppy, gambush and tilapia are destroying the ecosystem of the rivers.” 

According to a study by scientists from Hyderabad, Guwahati and Liverpool, rise in temperature results in a shorter ‘Extrinsic Incubation Period’ (EIP), which is the time required for the virus to develop in the mosquito. Shorter incubation period leads to higher transmission rate of dengue infection.

The start of this year was marked with resurgence of dengue cases, which are usually spotted after monsoon. There were 300 positive dengue cases recorded in Maharashtra in January this year, while in Pune 22 positive cases were recorded. 

The PMC has done its part by releasing guppy fishes into the river, as according to them the guppy fishes eat mosquito larvae.

But Ghate stated that guppy fish cannot reduce the population of malarial larvae. Instead, they are overpowering the native fishes of the rivers.

Ghate told Sakal Times that, till early 1970s all the rivers of the city were in a good state, but as the city started growing, pollution in river started increasing. In 1950 the civic body introduced tilapia fish for culture. Later, it grew in population and spread, which reduced the population of native fishes. Same was done with guppy and gambusia. Now, all three species are feeding on the native fishes, due to which the biodiversity of the local rivers is being affected.

“Another reason for the decline in population of native fish is due to massive amounts of sewage and industrial pollution released into Mula, Mutha and Pavana rivers. The Mutha is loaded with sewage while Mula and Pavana are polluted with a mixture of sewage and industrial toxics. All the data collected  indicates that the rivers are loaded with organic matter. Therefore, very little oxygen penetrates into the river and lack of oxygen kills the fish,” Ghate said.

- More than 60 types of native fishes were found in the rivers of the city.
- About 30 per cent, i.e 18 out of 60 that were reported earlier are not found now.
- Native fishes like loaches, prawns, bivalve and snail, all bottom dweller fishes have reduced in number.
- Singhara (Sperata seenghla), Kachaki (Chanda nama), Chilapi (Oreochromis mossambicus) and Punties (Puntius sophore) are some of the the prominent fish species found in Pune rivers, but nearing extinction.

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