Invasive Fish Species: Mosquito Control or Ecological Threat?

The National Green Tribunal (NGT) has sought a response from the Central Government regarding the use of two invasive fish species—Gambusia affinis and Poecilia reticulata—as biological agents for mosquito control in India.

Common Characteristics of Both Species

IUCN Status: Least Concern
Environmental Tolerance: Survive in brackish water, high salinity, and extreme temperatures.

---

Gambusia Affinis (Western Mosquitofish)

• Native Range: Mississippi River Basin, USA (from Indiana to the Gulf of Mexico).
• Habitat: Found in freshwater bodies, especially stagnant ponds and slow-moving streams.
• Key Characteristics:
  • Can survive in low oxygen environments.
  • Viviparous: Give birth to live young instead of laying eggs.
  • Aggressive nature: Preys on native fish and disrupts local biodiversity.
• Invasive Impact:
  • Listed among the 100 worst invasive species (IUCN).
  • Outcompetes native fish species and alters ecosystems.

---

Poecilia Reticulata (Guppy / Millionfish / Rainbow Fish)

• Native Range: Northern South America & Caribbean Islands.
• Habitat: Prefers shallow pools and streams.
• Key Characteristics:
  • Highly adaptable and rapidly reproducing species.
  • Used globally for mosquito larvae control.
  • Competes with native fish species for food and habitat.
• Invasive Impact:
  • Potential disruption of local aquatic biodiversity.
  • Known to cause imbalance in freshwater ecosystems.

---

Ecological Concerns & NGT's Response

• Although these species help in mosquito control, their aggressive nature threatens native aquatic life.
• NGT's inquiry highlights the need for environmental assessments before widespread introduction.

Extinction Filtering: The Silent Biodiversity Crisis

What is Extinction Filtering?
Extinction filtering is the gradual loss of species that are sensitive to human disturbances, leaving behind only those that can survive in degraded or altered environments.

Key Aspects of Extinction Filtering

 How It Works?

✔ Sensitive species disappear due to habitat destruction, pollution, or climate change.
✔ Resilient species dominate, leading to a more homogeneous ecosystem.
✔ Over time, biodiversity declines, and natural ecosystems become less stable.

Causes of Extinction Filtering

Deforestation & Habitat Loss – Conversion of forests into agriculture or urban spaces.
Pollution & Climate Change – Rising temperatures and pollutants affecting species survival.
Hunting & Poaching – Direct elimination of vulnerable species.
Fragmentation of Habitats – Breaking up of ecosystems into smaller, isolated patches.

Consequences of Extinction Filtering

Eosystem Weakening – Reduced resilience to environmental shocks.
Loss of Genetic Diversity – Making species more vulnerable to diseases.
Trophic Imbalance – Disrupting food chains and predator-prey relationships.
Decline in Ecosystem Services – Reduced carbon sequestration, pollination, and water purification.

Concern for Tropical Forests

Tropical forests are biodiversity hotspots, but extinction filtering is leading to:
Loss of rare and specialized species.
Dominance of generalist species, making ecosystems less diverse & functional.
Increased vulnerability to climate change & deforestation impacts.

Solutions & Conservation Strategies

Expanding Protected Areas – Strengthening conservation efforts beyond reserves.
Habitat Restoration – Reforesting degraded lands & creating wildlife corridors.
Regulating Human Activities – Sustainable land-use practices & stricter laws.
Biodiversity Monitoring – Identifying species at risk before extinction occurs.

Why This Matters?

If extinction filtering continues, future generations will inherit a less vibrant, less resilient planet, where ecosystems fail to sustain life as they once did. Urgent conservation actions are needed to reverse this silent biodiversity crisis.