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Subansiri River tributary, Arunachal Pradesh, India

India, Arunachal Pradesh, Changlang District

The floodplains and forested foot-hills of northeastern India, especially around Dibrugarh, Tinsukia, and Namdapha, experience monsoon-fed seasonal pools, slow-flowing tributaries, and forest swamp zones. These are shaded, leaf-litter rich, with driftwood, clayish or sandy beds, and minimal aquatic vegetation. Water is often slightly acidic and low-flow.

Submitted by: Shivansh Rajpoot
Approved by: Hans-Georg Evers & Friedrich Bitter

GPS: 27.5035915, 96.3764572

Geographical region: Southern Asia
Drainage Basin: Brahmaputra
River catchment
Water body type: River
Water body name: Noa Dihing
Water body part: Flood plain
Water body course: Middle course
Water body: tributary of: River
Tributary name: Brahmaputra

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Water Chemistry

Water information

Water type: fresh-water
Water color: Clear water
Water transparency: Medium
Concentration of sediments: Low
Water temperature: 24 °C
Water flow/curent: Slow

Chemical parameters

pH: 6.0
Conductivity: 100
GH: 125 mg/l
dGH
KH: 36 mg/l
dKH
Dissolved Oxygen: 95 %

Substrate in nature

Sand: Beige
Pebble/Gravel: None
Stone: Grey
Stone form: Roundish
Silt/Mud: None
Leaves: Few
Driftwood: Few
Submerged terrestrial vegetation: Yes

Aquatic Biotope

Date of collecting: 23/04/2025
Collecting area: Flooded area
Water depth: 2,0m
Air temperature: 26 °C
Sunlight: Partial shade

Environment

Environment

Untouched

Surrounding area

The biotope is based in the subtropical lowland forests of Arunachal Pradesh, India, near Namdapha National Park. This region, located in the Eastern Himalayas, is among the world’s biodiversity hotspots.

The area experiences high rainfall from May to October and maintains mild to warm temperatures year-round. Dense forest canopies shade narrow streams that flow through leaf-littered forest floors, supporting unique fish species including Channa bleheri. The region is largely untouched and home to elephants, hornbills, red pandas, and a vast diversity of insects and amphibia.

Underwater landscape

The watercourse is a slow-moving forest stream with a soft sandy-clay substrate, scattered with large amounts of leaf litter, driftwood, and some rounded stones. The water is lightly stained with tannins due to decaying plant matter.

Aquatic vegetation is sparse; instead, algae, periphyton, and fine detritus dominate. Floating debris and submerged roots offer natural hiding spots.

Visibility varies seasonally, with dry months offering clearer conditions. This environment suits Channa bleheri, which uses wood and leaves for cover and surface hunting.

Threats to ecology

Though some areas are protected, deforestation, mining, and agriculture are gradually encroaching upon Northeastern India’s natural waterways.

Road construction and illegal logging pose serious threats to aquatic biodiversity.

The introduction of exotic species and pesticide runoff further disrupt local ecosystems.

Conservation of pristine biotopes like this is vital not only for endemic fish such as Channa bleheri but also for countless lesser-known freshwater species dependent on stable forest stream environments.

Riparian zone

Trees near the aquatic habitat: Few - Shorea robusta (Dipterocarpaceae)
Trees near the aquatic habitat: Few - Ficus religiosa (Moraceae)

Bibliography

Smithsonian Contributions to Zoology - Channa bleheri by Sven O. Kullander
Zoological Survey of India - Snakehead Fishes of India by Ralf Britz
ISBN 9788181712703
Morphological notes on Channa bleheri by Ralf Britz