Gambusia: This solution could actually be an invasive problem

Subject :Environment

Section: Biodiversity

Context:

The Andhra Pradesh government has released approximately 10 million Gambusia fish into the state’s water bodies to combat mosquito-borne diseases like malaria and dengue.

Details:

Andhra Pradesh reported approximately 6,391 dengue cases and 2,022 malaria cases in 2022.

About gambusia fish:

The fish, also known as mosquitofish, is widely used as a biological agent for controlling mosquito larvae.
Gambusia affinis (G affinis) is native to the waters of the southeastern United States and a single full grown fish eats about 100 to 300 mosquito larvae per day.
G affinis has a sister species, Gambusia holbrooki (G holbrooki), also known as the eastern mosquito fish.
Mosquitofish has been part of various malaria control strategies in India since 1928, including the Urban Malaria Scheme.

Effectiveness of Gambusia fish:

While there are studies that showed reduction in malaria cases where the fish were introduced, there are others that reported increased mosquito larvae population where they were introduced, as the latter preyed on other predators that ate mosquito larvae.
There are also studies that reported that Gambusia’s predatory efficacy reduced when they were introduced in running water streams, water bodies with high insecticide levels and waterbodies with thick vegetation.

Highly invasive:

The fish has a high breeding capacity. A single female may produce between 900 and 1,200 offspring during its lifespan.
The International Union for Conservation of Nature has declared Gambusia one of the 100 worst invasive alien species in the world.
It is declared an invasive alien species in India as well.
They are known to eat the eggs of competing fishes and frog tadpoles.

WHO report on Gambusia fish:

A World Health Organization publication supported the effectiveness of breeding and use of G affinis as a larval control method in man-made breeding habitats, like swimming pools and garden ponds, with no access to the natural environment.
Instead of relying on Gambusia, the 2020 paper suggested encouraging “biologists and fish taxonomists to come up with river basin-based lists of native fish species that can control mosquito larvae and releasing them into the natural environment.”