The sighting of dead fish floating in Deepor Beel Wildlife Sanctuary, near Guwahati, has raised concerns about the health of Assam’s only Ramsar site. Some experts have suggested that seasonal feeding on aquatic plant seeds and the decomposition of submerged vegetation may explain the deaths. However, the exact cause should be confirmed through scientific investigation and water-quality testing rather than assumed to be entirely natural.

About Deepor Beel

• Deepor Beel, a freshwater ox-bow lake formed by the Brahmaputra, is one of Assam’s most ecologically important wetlands, spanning 4,014 hectares in southwestern Guwahati. 
• It holds multiple conservation recognitions—Wildlife Sanctuary (1989), Ramsar Site (2002), Important Bird Area (2004), and Eco-Sensitive Zone (2021).
• Biodiversity hosted by Deepor Beel: 435 plants; 219 algae; 24 dragonflies, 15 damselflies; 31 aquatic insects; 14 Protozoas; 78 birds.
• According to environmentalists, the eastern portion of the wetland has become severely polluted due to inflow from the Bharalu and Bahini rivers and runoff from a nearby municipal dumping ground.
  • The contamination is so intense that elephant herds from Rani and Gorbhanga forests have stopped drinking from the eastern side for the last three years.
• It is highlighted that nearly 80% of aquatic vegetation has vanished, including species such as:
  • Fox nut, singori, Water lily,  Water spinach, Nisala khar and Potol khar (key food for migratory birds and fish), Dol grass, a preferred elephant fodder
• This decline threatens both migratory birds and large mammals. Deepor Beel once hosted hundreds of birds; now, food scarcity and water toxicity may disrupt winter migrations.

Other Ramsar Sites in the Northeast 

• Loktak Lake – Manipur
• Rudrasagar- Tripura
• Pala – Mizoram

• Khachoedpalri – Sikkim
• Glaw Lake – Arunachal Pradesh

Why Are Fish Dying?

Environmental explanations reported in the recent incident include two possible natural processes.

• Aquatic plant seeds: Environmentalist Laxman Teron suggested that certain fish consume large quantities of ripe seeds from submerged aquatic plants during September and October, potentially causing fatal stomach swelling.
• Decomposing vegetation: Zoologist Dr Migrendra Mohan Goswami explained that post-monsoon decomposition of aquatic plants, including Najas indica and Hydrilla verticillata, creates organic debris that some fish consume excessively.

These explanations remain expert interpretations, not a substitute for site-specific testing. Pollution, low dissolved oxygen and other water-quality changes should also be investigated before the cause is conclusively established.

Major Threats to Deepor Beel

• Pollution: Untreated wastewater and solid waste entering the wetland can harm aquatic organisms and degrade water quality.
• Encroachment and urbanisation: Construction and changes in surrounding land use can reduce the wetland’s natural area and disrupt water flow.
• Infrastructure pressure: Roads, railway infrastructure and other development can fragment habitats and disturb wildlife.
• Ecological imbalance: Changes in water levels, excessive fishing and the spread of invasive aquatic plants can affect biodiversity.

Exam Hook: Key Takeaway

Deepor Beel demonstrates how wetlands support biodiversity, reduce urban flood risks and sustain livelihoods, while remaining vulnerable to pollution and unplanned development.

One-line Wrap: Protecting Deepor Beel requires scientific monitoring, pollution control and coordinated conservation to safeguard Guwahati’s natural wetland heritage.