The National Green Tribunal’s order in Original Application No. 718/2024 marks a watershed in India’s aquatic biodiversity jurisprudence. For the first time, a court has explicitly linked the decline of native fish populations to systemic failures in pollution control, infrastructure planning, and invasive species regulation - demanding coordinated, science-based intervention across multiple agencies.
Background & Facts
The Dispute
The case arose from a 2024 news report in Amar Ujala highlighting a dramatic ecological shift in the Yamuna River: a 70% decline in native fish species such as Mahseer, Rohu, and Catla, alongside a surge in invasive exotic species like Thai Mangur (Clarias gariepinus) and Nile tilapia. The Central Inland Fisheries Research Centre (CIFRI) confirmed through a three-year survey (2020 - 2024) that 126 fish species now inhabit the 1,368 km stretch from Yamunotri to Prayagraj, but native biodiversity is collapsing, particularly between Delhi and Mathura.
Procedural History
- May 2024: Tribunal took suo motu cognizance of the news report under Section 14 of the National Green Tribunal Act, 2010.
- July - November 2024: Notices issued to seven respondents including Ministry of Jal Shakti, CPCB, CIFRI, and State Fisheries Departments.
- December 2025: Final hearing concluded; order reserved.
- January 29, 2026: Order pronounced with comprehensive directions.
Relief Sought
The Tribunal did not entertain a traditional petition but exercised its suo motu jurisdiction to compel state and central agencies to reverse the ecological degradation of the Yamuna’s aquatic ecosystem, with a focus on restoring native fish populations and halting the spread of invasive species.
The Legal Issue
The central question was whether the decline of native fish species in a major river system constitutes a violation of the right to a healthy environment under Article 21 of the Constitution and whether state agencies have a non-delegable duty to enforce ecological flow, regulate invasive species, and restore aquatic biodiversity under the Environment (Protection) Act, 1986.
Arguments Presented
For the Petitioner (Tribunal acting suo motu)
The Tribunal relied on CIFRI’s empirical data showing that native carps reproduce only once annually at larger sizes, while exotic species like Thai Mangur breed rapidly at smaller sizes and tolerate low oxygen. It cited M.C. Mehta v. Kamal Nath to affirm that rivers are public trust resources requiring ecological protection. The Tribunal emphasized that the failure to enforce existing bans on exotic fish farming (per 1997 and 2019 directives) and lack of fish ladders at barrages violated the precautionary principle and polluter pays principle.
For the Respondent/State Agencies
Respondents acknowledged data accuracy but argued that: (1) pollution control is a complex, multi-jurisdictional challenge; (2) exotic fish proliferation is partly due to ritual releases and aquaculture escapes beyond state control; (3) existing ranching programs under PMMSY are ongoing and require time. They contended that no statutory mandate explicitly requires fish conservation as a standalone obligation.
The Court's Analysis
The Tribunal rejected the argument that ecological harm must be proven through litigation to trigger state duty. It held that biodiversity loss is itself a form of environmental degradation warranting immediate intervention. The Court examined the Designated Best Use Water Quality Criteria (Class D) under the Environment (Protection) Rules and found that 18 of 32 monitoring points failed Dissolved Oxygen norms - directly impairing spawning and survival of native species.
"The presence of exotic species is not merely an ecological curiosity; it is a symptom of systemic regulatory failure and a direct threat to the genetic integrity of native fish populations."
The Tribunal distinguished State of Himachal Pradesh v. Umed Ram (which focused on pollution alone) by emphasizing that habitat fragmentation from barrages and biological invasion are distinct but interlinked threats. It noted that while the Department of Fisheries had banned Thai Mangur farming since 1997, enforcement was absent, rendering the prohibition a "paper ban." The Court also affirmed that ecological flow (e-flow) is not discretionary but mandatory under the National River Conservation Plan.
The Tribunal further held that ranching without genetic safeguards risks hybridization and loss of native gene pools, citing CIFRI’s own guidelines. It rejected the notion that economic development justifies ecological sacrifice, invoking T.N. Godavarman Thirumulpad v. Union of India to affirm that environmental protection is a constitutional imperative.
The Verdict
The Tribunal ruled in favor of ecological integrity. It held that the state has a constitutional and statutory duty to restore native fish populations by enforcing pollution controls, banning invasive species, constructing fish passages, and implementing science-based ranching. All agencies were directed to comply with specific, time-bound measures within six months.
What This Means For Similar Cases
Ecological Flow Is Non-Negotiable
- Practitioners must now argue that any dam or barrage affecting migratory fish must include fish ladders as a mandatory condition under environmental clearances.
- Water allocation plans for irrigation or hydropower must now include minimum e-flow thresholds calibrated to fish spawning cycles.
Exotic Species Ban Must Be Enforced, Not Just Issued
- Paper prohibitions (e.g., bans on Thai Mangur since 1997) are legally insufficient. Practitioners can now file petitions for contempt or mandamus where bans are ignored.
- Aquaculture licenses must include physical containment requirements and post-flood monitoring protocols.
Biodiversity Metrics Must Inform Environmental Monitoring
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CPCB and state PCBs must now include fish species composition as a key biological indicator in water quality reports - not just chemical parameters.
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Environmental Impact Assessments for river projects must now include fish migration impact studies and invasive species risk assessments.
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Ranching programs must be genetically audited to prevent hybridization with native stocks.
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Public ritual releases of exotic fish must be criminalized under Section 27 of the Environment (Protection) Act.
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State Fisheries Departments must maintain digitized, location-specific catch data for evidence-based policy.
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Legal challenges to sand mining near spawning beds can now be grounded in fish habitat destruction, not just erosion or sedimentation.
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Academic institutions must now conduct long-term ecological studies on native-exotic interactions to support litigation and policy.
