Where Biodiversity and Livelihoods Meet
In the lush landscapes of Northeast India, water is more than just a resource—it's the lifeblood of ecosystems and communities alike.
Nestled in the northeastern corner of India lies a biological treasure trove of stunning diversity. This region, encompassing two of the world's 34 biodiversity hotspots—the Indo-Burma and Himalayan hotspots—hosts an extraordinary array of aquatic ecosystems including 19,150 km of rivers, 23,972 hectares of reservoirs, 143,740 hectares of lakes, 40,809 hectares of ponds, and even 2,780 hectares of rice cultivation fields that double as fish farming grounds 1 . These waters teem with life, including 520 fish species (35 of which are found nowhere else on Earth), 186 mollusc species, and 367 different dragonfly species 3 . Yet these precious ecosystems face mounting threats from climate change, human activities, and economic pressures, making their study and conservation more urgent than ever.
The northeastern Himalayan region of India represents a paradox of immense natural wealth existing alongside significant conservation challenges. Despite housing over 45% of India's freshwater fish species within its landlocked confines, the region contributes a mere 4.5% to the country's inland fish production 4 . This startling disparity highlights both the untapped potential and serious management issues plaguing these aquatic ecosystems.
The region's geography—surrounded by the Himalayan Mountain range in the north, the plains of Bangladesh to the south, the Burmese hills in the east, and additional hills and mountains in the west—has created uniquely heterogeneous habitats that have fostered remarkable speciation 4 . The plain areas of the Brahmaputra and Barak river systems, along with the Imphal valley and adjacent highlands, provide diverse ecological niches for aquatic life to flourish.
Beneath the water's surface exists an invisible world that forms the foundation of aquatic food webs—the phytoplankton. In the Maphou Reservoir of Manipur, researchers have identified an impressive 69 phytoplankton species, the highest recorded taxonomic diversity in any of the region's reservoirs . Bacillariophyceae (diatoms), represented by 30 species, showed the greatest diversity—a common feature of tropical reservoirs but remarkable nonetheless for a newly formed water body .
This plankton community displays fascinating seasonal dynamics, with abundance peaking during the monsoon season and reaching its lowest point in the post-monsoon period . The dominance of certain species like Ceratium hirundinella provides valuable clues about the reservoir's trophic state, indicating mesotrophic conditions (moderate nutrient levels) and an intermediate stage in the reservoir's ecological development .
| Parameter | Findings | Ecological Significance |
|---|---|---|
| Total species identified | 69 species | Highest recorded diversity in region's reservoirs |
| Most diverse group | Bacillariophyceae (diatoms) - 30 species | Typical of tropical reservoirs; key primary producers |
| Seasonal abundance | Highest in monsoon, lowest in post-monsoon | Reflects nutrient influx and environmental conditions |
| Dominant species | Ceratium hirundinella (59.88% of total) | Indicator of mesotrophic state and intermediate succession stage |
| Spatial distribution | Highest near dam site | Influenced by depth, human activity, and water dynamics |
Recognizing the critical importance of these aquatic ecosystems, the "Protection and Sustainable Management of Aquatic Resources in the North-Eastern Himalayan Region of India" (NERAQ) project was implemented from 2020 until mid-2025 1 . This ambitious initiative, financed by the International Climate Initiative and implemented by Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH in close cooperation with Indian and German environment ministries, took a comprehensive approach to conservation 1 5 .
One of the project's most innovative aspects was its integration of indigenous knowledge with contemporary scientific approaches. In Nagaland, the village community of Poilwa demonstrated sophisticated ecological understanding through their use of biodegradable fishing equipment and fishing practices aligned with the lunar calendar—methods that harmonize perfectly with climate-conscious strategies 1 . The worth of this indigenous knowledge was recognized by Kohima Science College, which integrated it into their standard curriculum to preserve it for future generations through formal education 1 .
The project also documented traditional knowledge in four pilot areas, compiling this profound understanding of aquatic ecosystems into a methodological manual that was added to the collection in a newly established visitors' centre near Khliehshnong, Meghalaya, in March 2025 1 . This preservation of knowledge is crucial for maintaining cultural heritage alongside biological conservation.
The NERAQ project achieved remarkable success by empowering local communities to become guardians of their aquatic resources:
These community-driven initiatives demonstrate that when local populations are empowered with knowledge and resources, they can become the most effective stewards of their natural heritage.
Project implementation begins with focus on community engagement and baseline assessments.
Documentation of traditional knowledge in four pilot areas; establishment of protected zones in Nagaland and Manipur.
Establishment of the regional knowledge network "North East India Freshwater Collective" in November 5 .
Project concludes; methodological manual added to visitors' centre in Meghalaya in March 1 .
To understand how scientists study these complex aquatic ecosystems, let's examine a detailed investigation into phytoplankton communities in Northeast India's reservoirs.
A comprehensive study conducted from June 2021 to May 2022 in the Maphou Reservoir systematically analyzed how phytoplankton communities respond to changing environmental conditions . Researchers collected water samples monthly from four strategically chosen locations representing different ecological zones: near the dam (the deepest area), near cage culture operations, near a tourist spot, and in the mid-stream region .
At each site, scientists measured crucial water quality parameters including temperature, pH, electrical conductivity, transparency, dissolved oxygen, and various nutrient levels . They simultaneously collected phytoplankton samples by filtering 50 liters of sub-surface water through specialized mesh, preserving the concentrates for detailed laboratory analysis where identification and counting were performed using advanced microscopic techniques .
| Diversity Index | Range Observed | Interpretation |
|---|---|---|
| Shannon-Wiener Index (H') | 1.1 to 2.19 | Moderate diversity across sites and seasons |
| Margalef Richness (d') | 3.06 to 4.76 | Moderate species richness |
| Pielou's Evenness (j') | 0.303 to 0.593 | Moderate distribution of individuals among species |
The investigation yielded fascinating insights into the complex relationship between environmental factors and phytoplankton communities. Statistical analysis revealed that total phytoplankton abundance showed positive correlations with water temperature, alkalinity, phosphate (PO₄-P), and nitrite (NO₂-N) . More sophisticated Canonical Correspondence Analysis identified electrical conductivity, total alkalinity, transparency, nitrate (NO₃-N), and phosphate (PO₄-P) as the key abiotic factors shaping the phytoplankton community structure .
Perhaps most notably, the research documented the highest phytoplankton abundance near the dam site, followed by mid-stream shallow regions and areas with significant human intervention such as tourist areas and cage culture sites . This spatial pattern underscores how both natural gradients and human activities collectively influence the foundation of aquatic food webs.
Phytoplankton abundance peaks during monsoon season and reaches lowest point in post-monsoon period .
| Tool/Technique | Primary Function | Application in Northeast Indian Context |
|---|---|---|
| Niskin Sampler | Collects water samples at specific depths | Used for sampling in Ratnagiri coastal waters 2 |
| Sedgwick-Rafter Slide | Microscopic identification and counting of phytoplankton | Employed in Maphou Reservoir study |
| High-Performance Liquid Chromatography (HPLC) | Pigment analysis and phytoplankton group identification | Applied for pigment profiling in Ratnagiri 2 |
| Spectrophotometry | Measures absorption properties of CDOM and phytoplankton | Used to analyze optical properties in coastal waters 2 |
| Lugol's Iodine Solution | Preserves phytoplankton samples for later analysis | Standard preservation method in reservoir studies |
| Secchi Disk | Measures water transparency | Critical for light availability assessment |
| IoT-based Water Monitoring | Real-time tracking of water quality parameters | Emerging technology provided to villages 1 9 |
Advanced tools like Niskin samplers enable precise collection at various depths.
Sedgwick-Rafter slides facilitate detailed phytoplankton identification.
Real-time water quality tracking enhances conservation efforts.
The pressure on Northeast India's aquatic resources is particularly intense given the region's nutritional dependencies and economic aspirations. Approximately 97% of the region's population are fish eaters, with a per capita fish consumption of about 10.9 kg 4 . Yet the region's average fish productivity stands at just 1.5 MT/hectare/year, significantly below the national average of 3 MT/hectare/year 4 .
This production gap presents both a challenge and an opportunity. The NERAQ project addressed this by promoting sustainable alternative livelihoods such as weaving, piggery, poultry farming, and snail and fish farming in rice cultivation areas 1 . These approaches reduced dependence on wild-caught products and consequently eased pressure on natural ecosystems 1 .
Meanwhile, innovative aquaculture technologies like Bio Floc Technology and Recirculatory Aquaculture Systems are emerging in the region, offering promising pathways to enhance productivity without exacerbating environmental degradation 4 . These systems, particularly when integrated with traditional knowledge, represent the future of sustainable aquatic resource management in Northeast India.
The aquatic ecosystems of Northeast India stand at a critical juncture. Climate change, anthropogenic pressures, and economic development needs pose significant threats, yet the region's ecological richness and cultural wisdom provide strong foundations for building a sustainable future.
The success of the NERAQ project demonstrates that community-driven conservation, backed by scientific research and traditional knowledge, can yield impressive results 1 5 . The discovery of two new fish species and four aquatic insects during the project's inventory activities in Nagaland underscores how much remains to be learned about these biologically rich ecosystems 5 .
As we move forward, the integration of advanced technologies like IoT-based water monitoring 9 with indigenous practices such as the lunar-based fishing calendar of Poilwa 1 offers the most promising approach to conservation. The establishment of the regional knowledge network "North East India Freshwater Collective" in November 2024 represents a crucial step in this direction, ensuring that collaboration and knowledge sharing will continue to guide the stewardship of Northeast India's precious aquatic resources 5 .
Engage local communities as guardians of aquatic resources.
Blend traditional wisdom with scientific research.
Develop eco-friendly fish farming practices.
Establish knowledge-sharing platforms like the Freshwater Collective.
The future of Northeast India's wetlands, rivers, fish, and plankton resources depends on our ability to balance human needs with ecological integrity—a challenge that requires honoring both traditional wisdom and modern science in equal measure.