What is invasive alien species?
An invasive alien species is a plant, animal, or other organism that is introduced outside its native range and becomes overpopulated, causing harm to the new environment.
They are one of the biggest threats to biodiversity worldwide, causing ecological, environmental, and economic damage.
key characteristics of invasive alien species:
Introduced: They are not native to the new environment and were brought in by human activities, either intentionally (e.g., for landscaping or pest control) or accidentally (e.g., through trade or travel).
Overpopulated: They reproduce and spread rapidly in the new environment, often due to a lack of natural predators or competitors.
Harmful: They have negative impacts on the new environment, such as:
Outcompeting native species for resources like food and space.
Predating on native species.
Transmitting diseases to native species.
Disrupting natural ecosystems and ecosystem functions.
Causing economic damage, for example, by damaging crops or infrastructure.
What is mosquitofish?
In this milieu, the biological control of mosquitoes assumes importance.
In the 1960s, such approaches – including introducing mosquitofish in freshwater ecosystems to feed on mosquito larvae – became prominent as alternatives to chemical solutions like pesticides, which were found to have dire adverse effects on both human health and the ecosystem.
The uptake of these alternatives increased in the 1980s and 1990s.
Many of them were considered to be environmentally friendly and sustainable.
Among mosquito predators were two species of mosquitofish, Gambusia affinis and Gambusia holbrooki.
In countries with governments that had approved this strategy, the authorities released them into freshwater ecosystems.
What they didn’t plan for, however, was that the fish began to proliferate here, with their populations eventually spreading far beyond their original habitats.
These species of mosquitofish originated in the U.S. but today have become global inhabitants.
They are notorious for their detrimental ecological impact, including displacing and preying on native fauna, leading to the extinction of native fish, amphibians, and various freshwater communities.
As such, Gambusia stands out as some of the most widely dispersed freshwater fish, aided by their robust adaptability and high tolerance for fluctuating environmental conditions.
Is mosquitofish ‘used’ in India?
The ICMR, India’s nodal medical research organisation, plays a significant role in mosquito management in the country.
In the context of controlling mosquito-borne diseases and conducting research to develop effective strategies.
In 1928, Gambusia was first introduced in India during British rule.
Later, various governmental organisations, such asthe ICMR, the National Institute of Malaria Research (NIMR), local municipal corporations, the Fisheries Department, and the Health Department, alongside other private organisations in India, took over as part of their efforts to combat malaria.
The idea of this scheme was that the newly introduced species would prey on or compete with mosquito larvae, reducing the latter’s population.
The government also entrusted several municipal corporations, district administrations (and their health departments), fisheries departments, tribal development agencies, local aquaculturists, and the general public with introducing these fish across India.
Today, as in the American story, Gambusia, has become widespread in India as well, establishing self-sustaining populations in various habitats around the country.
The strategy was well-intentioned but it backfired, leading to severe ecological and environmental problems.
How can mosquitofish be controlled?
The problem today is both wolf at the door and termites at the base, and the optimal solution needs practitioners to tackle the problem from multiple angles.
The first has to do with the National Centre for Vector Borne Diseases Control – of the Ministry of Health & Family Welfare – displaying a recommendation on its website for the use of Gambusia and Poecilia (guppy) fishes to manage mosquitoes.
Second, for effective mosquito control, alternatives to Gambusia should come from local solutions.
Experts have suggested a collaboration between mosquito biologists/entomologists, invasion ecologists, and fish taxonomists, with a focus on river basins.
Together, they can compile lists of native fish species in each basin that are capable of controlling mosquito larvae.
Then, based on these lists, authorities can release the relevant species into the natural environment, sidestepping the risk of ecological repercussions posed by invasive alien species.
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