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