The scale of the human stakes is enormous. India is the world’s second-largest fish producer, with a record 175.45 lakh tonnes of fish production in 2023, and its fisheries sector has grown by 10.87 percent since 2014–15. Odisha alone produces roughly 8.73 lakh metric tonnes annually, drawing on a 480 kilometre coastline and nearly 11 lakh hectares of inland and brackish waters. Globally, small-scale fisheries account for more than 90 percent of active fishers and support nearly two-thirds of the global fish catch, yet they remain chronically underreported in statistics and overlooked in policy. Chilika exemplifies this blind spot: more than 400,000 fishers live in nearly 150 settlements around the lagoon, many operating under a unique governance system that grants exclusive fishing rights administered through cooperatives and supported by the Chilika Development Authority.

Salinity in Chilika is governed by a delicate tug-of-war between seawater pushing in through tidal inlets from the Bay of Bengal and freshwater discharging from inland rivers. The lagoon spans nearly 1,100 square kilometres during the monsoon and contracts to about 906 square kilometres in the dry months, with an average depth of just 1.8 metres. This shallow, hydrologically dynamic system is divided into four ecological sectors: the freshwater-dominated Northern Sector, the Central and Southern Sectors, and the saline-rich Outer Channel. Seasonal salinity ranges from nearly zero during the rains to around 17 parts per thousand in winter and roughly 35 parts per thousand in summer, creating one of the steepest estuarine gradients in Asia and a natural laboratory for studying how salt shapes biodiversity.

The historical record reveals dramatic swings. Average salinity fell from 22.3 parts per thousand in 1957–1958 to between 9.4 and 11.8 parts per thousand by the early 1960s, and dropped to a critical low of 8.3 parts per thousand by 1999. The culprit was partly geomorphological: the commissioning of the Hirakud Dam on the Mahanadi River in 1957 unexpectedly increased the silt load entering the lagoon, driving progressive sedimentation, choking of the Arakhakuda mouth, reduced tidal exchange, salinity decline, and rampant weed overgrowth. In response, an artificial sea mouth was opened near Sipakuda village on 23 September 2000, restoring seawater ingress. Natural inlets subsequently formed at Gabakunda in 2008, Dhalabali in 2012, and during Cyclone Phailin in October 2013, and research by Panda and Mohanty showed that the shift from a single to a multiple inlet system between 2006 and 2009 produced pronounced changes in annual mean salinity, with cascading effects on sedimentation, marine species intrusion, and ecological balance.

Extreme weather adds another layer of volatility. The Super Cyclone of 1999 devastated fisheries resources and infrastructure. Cyclone Phailin in 2013 triggered a dramatic post-monsoon salinity decline and altered nutrient concentrations, lowering phosphate and nitrate while raising silicate and ammonia. Cyclone Fani in 2019, striking in May during the lagoon’s peak salinity period, instead elevated salinity relative to other storms, while Hudhud in 2014 had minimal impact. Data from 1999 to 2021 show average salinity of 10.69 parts per thousand, ranging from 0.1 to 36.9, with the Northern Sector experiencing sharp fluctuations and the Southern Sector remaining more stable. Most recently, a deep depression over the northwestern Bay of Bengal on 13 July 2022 opened a new inlet, driving Outer Channel salinity from 21 to 34 parts per thousand in June down to zero to 2 parts per thousand by August. Broader climate phenomena, including the El Niño–Southern Oscillation, modulate these patterns by influencing precipitation, river discharge, and lagoon–sea exchange.

The biological consequences are striking. Fish diversity in Chilika is structured along the salinity gradient: freshwater species dominate the north, brackish species the centre and south, and the tidal Outer Channel supports both brackish and marine fishes. Species counts have climbed from 138 aquatic species recorded in 1918 to 336 by 2008, including 261 finfish, 28 prawns, and 34 crabs, before slipping slightly to 317 in 2023 across 207 genera, 88 families, and 23 orders. The lagoon also shelters around 700 plant and 800 animal species, including the endangered Irrawaddy dolphin, and serves as a critical stopover on the Central Asian Flyway for migratory birds. Salinity shifts impose oxidative stress on aquatic organisms, altering survival, reproduction, and distribution, and declining salinity has stressed brackish biota such as prawns, which form the backbone of the local fishery.

The 2000 hydrological intervention, however, demonstrates that salinity management can also drive recovery. Enhanced seawater exchange improved recruitment of juvenile marine fish, lifting fish landings from 11,989 metric tonnes in 2001–02 to 14,228 metric tonnes in 2011–12, documenting 56 new species, and coinciding with the reappearance of the Irrawaddy dolphin. Phytoplankton communities responded too: diatoms replaced cyanobacteria and came to dominate up to 72 percent of phytoplankton biomass, benefiting fish production. After the new inlet opened in July 2022, landings rose to 223.62 metric tonnes, with mullets and other marine species featuring prominently. Yet fishers also reported disturbances, including sand infestation, fluctuating water depths, and the arrival of unfamiliar marine organisms such as stingrays, octopuses, and jellyfish, which reshaped fishing seasons and species composition.

Habitat degradation compounds the problem. Declining salinity converts brackish habitats into freshwater-dominated systems, eliminating niches for estuarine species such as mullets and anchovies, narrowing tidal channels, and degrading seagrass meadows that serve as critical spawning and feeding grounds for prawns and crabs. Long-term desalination has fuelled invasive weed growth, particularly in the northern sector, while excessive sedimentation and intensive prawn aquaculture, locally known as gheri or bund fishing, have altered hydrology and sediment transport, impeding fish migration and nutrient flow. Embankments and dams further disrupt natural flow, fragmenting habitats and reducing species resilience. The socioeconomic fallout is cascading: declining catches and unstable incomes exacerbate poverty, malnutrition, and occupational migration, and in some cases entire villages have shifted away from fishing altogether, while shrimp aquaculture introduced in the 1980s disrupted traditional access rights and intensified competition.

The review’s authors frame salinity not merely as a physical parameter but as a socio-ecological determinant linking ecological balance with human well-being, and they chart a path forward. Key strategies include restoring ecological buffers such as mangroves, seagrass beds, and wetlands that stabilize salinity and provide fish nurseries; promoting livelihood diversification through eco-tourism, aquaculture, and small enterprises; enforcing fisheries laws such as the Marine Fishing Regulation Acts in collaboration with local communities; and building fisher capacity in adaptive practices like seasonal restrictions, spatial management, and catch diversification. Regular monitoring of salinity and hydrological parameters is deemed indispensable for guiding adaptive management, and economic valuation shows fishery resources account for over 71 percent of the lagoon’s total economic value, underscoring what is at stake.

Ultimately, the study lays the groundwork for future econometric analyses quantifying how salinity variation cascades through biodiversity and artisanal livelihoods. As climate change accelerates sea-level rise, saltwater intrusion, and cyclone intensity across low-lying Asian coasts, Chilika’s experience offers a cautionary tale and a template: salinity management, if pursued inclusively and grounded in fishers’ rights, can allow Asia’s largest brackish water lagoon to thrive both as an ecological jewel and as a lifeline for the communities whose fortunes rise and fall with its salt.

Subject of Research: Salinity dynamics and their ecological and socioeconomic impacts on artisanal fisheries in Chilika Lagoon, India

Article Title: Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon

Article References: Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon. (n.d.). https://doi.org/10.1007/s44289-026-00137-1

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00137-1

Keywords: Chilika Lagoon, salinity, artisanal fisheries, brackish water, climate change, biodiversity, tidal inlets, cyclones, Odisha, small-scale fisheries, habitat degradation, hydrology

The research, led by Navya Vikraman Nair of the University of Waterloo together with Jeremy Pittman and Prateep Kumar Nayak, examines how local ecological knowledge, often abbreviated as LEK, can inform participatory biodiversity monitoring in a climate-vulnerable blue carbon ecosystem. Blue carbon ecosystems, which include seagrasses, salt marshes, and mangroves, are among the planet’s most effective natural carbon sinks, but they are also among the most rapidly disappearing. Global assessments have documented accelerating losses of seagrass meadows worldwide and a rising pace of human impact on the ocean, making robust monitoring urgently important. In many data-limited regions, however, the ecological baselines needed to detect change simply do not exist, and that is precisely the gap the researchers set out to explore.

To gather evidence, the team combined structured surveys involving 47 participants with semi-structured interviews and participatory ranking exercises involving 28 fishers and other lagoon-dependent stakeholders. This dual approach allowed the researchers not only to document what people were observing in the lagoon but also to understand which observations communities themselves considered most important to monitor. The methodological design reflects a growing recognition in the environmental social sciences that monitoring is not merely a technical exercise but a social process, shaped by whose knowledge counts, whose priorities are heard, and who benefits from the resulting data.

The findings are striking in their breadth. Participants reported changes spanning six ecological and environmental domains: biodiversity, the condition of blue carbon ecosystems, water quality, ecosystem functions, climate and hydrological change, and anthropogenic and governance pressures. In other words, the fishers and other residents of Chilika were not simply reporting on fish catches. Their observations extended to the health of seagrass beds, the salinity and clarity of the water, the timing of seasonal floods, the behavior of migratory species, and the effects of management decisions on the lagoon’s ecology. This multidomain richness suggests that local knowledge can capture dimensions of ecosystem change that conventional monitoring programs, often constrained by budget and personnel, routinely miss.

From this empirical material the researchers developed what they call the LEK Ecological Indicator Wheel, a conceptual framework for organizing LEK-derived observations and potential monitoring variables. The framework arranges participant-reported observations across the six domains, providing a structured way to translate lived experience into candidate indicators for future monitoring programs. Crucially, the authors are careful about what the wheel is and is not. It is not a validated ecological index, and the observations it organizes are candidates for future monitoring and ecological testing rather than established measurements. This distinction matters, because the scientific credibility of community-derived indicators depends on rigorous validation against independent ecological data.

The study also confronts an important limitation with unusual candor. Although the instrument addressed multiple taxonomic groups, the prioritized observations turned out to be predominantly fisheries oriented. Fishers, naturally enough, notice what affects their livelihoods: the abundance of fish, prawns, and crabs, the state of the habitats that support them, and the water conditions that determine productivity. This orientation limits the extent to which the findings can support inference about lagoon-wide biodiversity, since birds, benthic invertebrates, and other components of the ecosystem receive less attention. The authors acknowledge this constraint explicitly, and it highlights a broader challenge for community-based monitoring: the knowledge a community holds reflects the relationships that community has with its environment, and those relationships are often selective.

Why does this matter beyond Chilika? The answer lies in the global context of biodiversity governance. The Kunming-Montreal Global Biodiversity Framework commits nations to halting and reversing biodiversity loss, and meeting those commitments will require monitoring at scales and in places where professional scientific capacity is thin. Multicountry assessments have shown that local communities can monitor tropical resources with accuracy comparable to professional scientists, and recent work argues for involving citizens directly in tracking progress toward global biodiversity targets. In this light, the Chilika study offers a template for how LEK might be systematically harvested, organized, and tested in blue carbon ecosystems around the world, from Southeast Asian seagrass meadows to West African mangrove deltas.

The technical logic of the approach deserves attention. Structured biodiversity monitoring, as the monitoring literature emphasizes, requires clear objectives, repeatable methods, and indicators that respond predictably to ecological change. LEK-derived observations can enter this machinery at the indicator-selection stage, where they can suggest variables that scientists might not have thought to measure, flag changes that occurred before formal monitoring began, and identify spatial and temporal patterns worth investigating. Participatory ranking exercises add a second layer of value by revealing community monitoring priorities, which can align research agendas with local needs and increase the legitimacy and durability of monitoring programs. When communities help choose what is measured, they are more likely to sustain the measurement over time.

There are also deeper epistemological stakes. Scholars of traditional ecological knowledge have long argued that ignoring fishers’ knowledge means missing the boat, both figuratively and literally, because resource users accumulate observations across seasons and decades that no research program could replicate. Frameworks such as the multiple evidence base approach call for connecting diverse knowledge systems on equal footing rather than treating local knowledge as raw material to be extracted and validated by science. The Chilika study sits squarely within this tradition, but it pushes further by attempting to structure LEK into a form that can interface with formal monitoring design, a step that many earlier studies stopped short of taking.

The path forward, the authors argue, requires two things: ecological validation and community co-design. Validation means testing LEK-derived indicators against independent ecological measurements to establish their reliability and sensitivity. Co-design means involving fishers and other stakeholders in every stage of developing monitoring programs, from selecting indicators to interpreting results to shaping management responses. If both conditions are met, LEK-derived observations could complement conventional monitoring, strengthen participatory assessment, and support adaptive management in climate-vulnerable blue carbon ecosystems. For Chilika Lagoon, whose social-ecological history includes dramatic hydrological interventions and contested governance, that prospect is more than academic. For coastal communities worldwide watching their seagrasses thin and their catches shift, the study offers a hopeful message: the people who live closest to change may hold some of the most valuable data about it, provided science learns to listen systematically and communities remain partners rather than subjects.

Subject of Research: Local ecological knowledge for participatory biodiversity monitoring in the blue carbon ecosystems of Chilika Lagoon, India

Article Title: Can local ecological knowledge inform biodiversity monitoring in climate-vulnerable blue carbon ecosystems?

Article References: Can local ecological knowledge inform biodiversity monitoring in climate-vulnerable blue carbon ecosystems?. (n.d.). https://doi.org/10.1007/s10113-026-02699-4

Image Credits: AI Generated

DOI: 10.1007/s10113-026-02699-4

Keywords: local ecological knowledge, biodiversity monitoring, blue carbon ecosystems, Chilika Lagoon, seagrass, small-scale fisheries, community-based monitoring, climate change, participatory research, adaptive management, water quality, Regional Environmental Change