News Excerpt:

A new study has revealed that two species of mosquitofish have invaded various ecosystems across India.

• To combat the mosquito problem that residents have been complaining about, a number of governmental and non-governmental organisations in Andhra Pradesh, Odisha, and Punjab have released mosquitofish into nearby water bodies in recent months.

About Mosquitofish:

• This mosquitofish is introduced in freshwater ecosystems to feed on mosquito larvae.
• It can live in shallow waters and travel through thick vegetation to reach the hiding places of larvae and pupae.
• It can withstand various environmental challenges, including shifting temperatures, organic pollutants, and food scarcity.
• Gambusia affinis and Gambusia holbrooki are two species of mosquitofish.
• Although these mosquitofish species were first found in the United States, they are now found worldwide.
• Mosquitofish Biology:
  • Maximum size of about 2 inches in length
  • Live 2-3 years, but may exceed this lifespan if conditions are favourable.
  • Give birth to live young
  • Produce up to 3-5 broods per year

Gambusia affinis:

• It is an exotic species distributed throughout the warmer and temperate parts of the world.
• The optimum temperature for reproduction ranges from 24 degrees Celsius to 34 degrees Celsius, but the fish can survive at freezing temperatures. 
• The maximum size attained by a male is 4.5 cm, and by a female, it is 5.2 cm to 6.8 cm. Its life span is approximately 4+1 years.
• The female matures in about 3 to 6 months. A single female may produce between 900 and 1200 offspring during its lifespan.

Is mosquitofish ‘used’ in India?

• India's central medical research body, the Indian Council of Medical Research (ICMR), is heavily involved in mosquito management in the nation.
• It helps prevent diseases spread by mosquitoes and carries out studies to provide practical countermeasures.
• Gambusia was first introduced to India in 1928, during the British reign.
• The plan was for the newly introduced species to prey on mosquito larvae, decreasing the latter's number. 

Impact of mosquitofish:

• Wildlife experts say mosquitofish are among the top 100 harmful invasive alien species.
• These fish have voracious eating habits and aggressive behaviour in newly introduced habitats.
• Studies in different nations have repeatedly demonstrated the detrimental effects of Gambusia in water bodies.
• For instance, the local extinction of the endemic red-finned blue-eye (Scaturiginichthys vermeilipinnis) fish species in Australia resulted from the introduction of mosquitofish.
• They have also been seen feeding on native fish and frog eggs and larvae.
• A New Zealand study brought attention to the danger Gambusia poses to the aquatic biodiversity that is native to that country.
• There have been reports of a decrease in Microhyla tadpoles in India after Gambusia was introduced.
• Due to these factors, Gambusia was no longer recommended by the World Health Organisation as a mosquito control agent in 1982.
• In 2018, the government of India's National Biodiversity Authority declared G. affinis and G. holbrooki as invasive alien species.

How can mosquitofish be controlled?

• Stricter enforcement measures are imperative to prevent the species from continuing to be introduced to freshwater ecosystems.
• Biologists and fish taxonomists suggested developing river basin-based lists of native fish species that can control mosquito larvae.