The National Green Tribunal (NGT) has sought a response from the Central government regarding the introduction of two invasive fish species—Gambusia affinis (Mosquitofish) and Poecilia reticulata (Guppy)—as biological control agents against mosquito populations in multiple Indian states, including Assam, Arunachal Pradesh, Gujarat, Karnataka, Maharashtra, Rajasthan, Tamil Nadu, Uttar Pradesh, Odisha, Punjab, and Andhra Pradesh.
The plea, filed before the Tribunal, raises concerns about the ecological damage caused by these non-native fish species and their adverse impact on India’s aquatic biodiversity. The NGT has now directed the respondents to file their reply regarding the scientific basis, ecological risks, and justification for continuing the practice of introducing these species into Indian water bodies.
NGT’s Concerns on Invasive Fish in Mosquito Control
The use of Gambusia affinis (Mosquitofish) and Poecilia reticulata (Guppy) as mosquito control measures has been widely practiced in several Indian states. These fish are known for their ability to consume mosquito larvae, which can help in reducing vector-borne diseases such as malaria, dengue, and chikungunya.
However, the National Biodiversity Authority (NBA) has categorized these species as “invasive and alien”, stating that their unregulated introduction into local water bodies has led to:
- Displacement of native fish species, causing food scarcity for indigenous aquatic life.
- Uncontrolled proliferation, leading to changes in local ecosystem dynamics.
- Negative impact on water quality and increased competition with native predatory species.
- Reduced effectiveness over time, as mosquito populations develop resistance to predation.
The plea before the NGT also noted that many countries, including Australia and New Zealand, have banned Mosquitofish due to their destructive impact on local fish populations and aquatic ecosystems.
States Affected by the Introduction of Mosquitofish & Guppy
According to the petition, the Mosquitofish (Gambusia affinis) has been introduced in the following states:
- Assam
- Arunachal Pradesh
- Gujarat
- Karnataka
- Maharashtra
- Rajasthan
- Tamil Nadu
- Uttar Pradesh
- Odisha
- Punjab
- Andhra Pradesh
Similarly, Poecilia reticulata (Guppy) has been released in Maharashtra, Karnataka, Punjab, and Odisha.
While these measures were introduced to control mosquito larvae, the long-term environmental consequences of their release have raised serious concerns among environmentalists, scientists, and conservationists.
Scientific Concerns About the Use of Invasive Fish
Many scientific studies have cautioned against the use of non-native species for biological control, citing unintended ecological consequences. Some of the major concerns include:
1. Impact on Native Biodiversity
Both Mosquitofish and Guppy are known for their aggressive feeding behavior. They compete with native fish species for food and can outnumber and outcompete local species, leading to a decline in biodiversity.
2. Disruption of Aquatic Ecosystems
Introducing non-native species can alter the natural food chain and disrupt the delicate balance of ecosystems. Indigenous fish species, which have evolved to coexist with local predators and prey, may struggle to survive alongside highly adaptable invasive species.
3. Ineffectiveness in Long-Term Mosquito Control
Studies have shown that Gambusia affinis and Poecilia reticulata are not always effective in reducing mosquito populations. Mosquitoes can develop behavioral resistance to these predators, rendering them inefficient in long-term vector control programs.
4. Increased Spread of Disease
Ironically, some studies suggest that Gambusia affinis may actually increase the risk of disease transmission by consuming the larvae of other insect species that naturally control mosquitoes. This creates an imbalance in the ecosystem, leading to higher mosquito populations in some cases.
5. International Precedents & Bans
Several countries have already banned or severely restricted the use of Mosquitofish due to its harmful environmental impact. Australia and New Zealand, in particular, have highlighted severe declines in native fish populations due to the introduction of Mosquitofish.
NGT’s Directive & Legal Proceedings
In an order dated January 24, the NGT bench, led by Chairperson Justice Prakash Shrivastava and expert member A Senthil Vel, issued a notice to the Central government, directing the respondents to file a reply.
The Tribunal has sought detailed information on:
- The justification for using invasive fish species in mosquito control programs.
- Scientific studies supporting their effectiveness.
- Ecological impact assessments conducted before their introduction.
- Alternative vector control measures being considered.
The outcome of this case could lead to policy changes regarding the use of biological control agents for mosquito population management in India.
Alternative Mosquito Control Strategies
Given the ecological risks associated with Mosquitofish and Guppy, experts have suggested alternative mosquito control measures, such as:
- Habitat Management – Eliminating stagnant water bodies, where mosquitoes breed, through better drainage and urban planning.
- Native Fish Species – Using local predatory fish that naturally feed on mosquito larvae, rather than relying on invasive species.
- Larval Source Management (LSM) – Using biological larvicides that specifically target mosquito larvae without harming other aquatic life.
- Public Awareness Campaigns – Encouraging communities to adopt preventive measures, such as using mosquito nets and repellents.
The NGT’s intervention highlights the critical need for sustainable and ecologically responsible mosquito control measures. While vector-borne diseases remain a major public health concern, the solution should not come at the cost of environmental degradation.
With multiple states affected by the introduction of invasive fish species, the NGT’s ruling could lead to nationwide reforms in mosquito control policies. The response from the Central government will play a crucial role in determining whether Gambusia affinis and Poecilia reticulata continue to be used or if India moves towards more sustainable and environment-friendly alternatives.